this manga has a death grip on me

Regarding the parallels, they both seem to be fairly similar to their fathers in general attitude, as is given in the few scenes we have of them; Yoshiki and his father are quieter and gloomy, while Hikaru and Kouhei are more friendly, cheerful and (seemingly) open about their emotions. And you can interpret further from what we know of og Hikaru and Yoshiki on the similar dynamics between the two, such as in the way that Hikaru's cheerfulness is used as a mask for repressing negative emotions (ie, Yoshiki never seeing Hikaru crying- even after his dad dies, such as Hikaru's joke at the gravestone about eating the offerings to lighten the mood) which I wouldn't be surprised Kouhei would've used. It's clear how strongly he felt about ending the passing down of the ritual, even fighting with the elders about it, but seems to be in the flashbacks always be cheerful, and seems quite flippant/over dramatic he seems when he's younger in telling the story of the sins of the Indou... even though he clearly takes the story to heart with the way he's asked the girl out many many times, and when point blank asked by Toshinori, admits that he's is, but it's 'just something he has to shoulder'. Meanwhile, Yoshiki hates the country and wants to leave because he feels that there is no place for him there; and this feeling of failing to belong is one that Toshinori also feels. This is evident when he talks about not feeling like he has a place within the family, implying he never felt like he had a place here to begin with as he comments that what people crave is often what people have never had in the first place. Quite interestingly, for Yoshiki, feeling like he doesn't belong is directly tied to him being queer; that sentiment being directly echoed by Toshinori, implies that Toshinori's own feelings may also arise from being queer... something strengthened by the relationship Toshinori and Kouhei had.

Page 1: where Toshinori says that people always yearn for what they don't have, after talking about being afraid of not belonging in their house, also indicating he likely never really felt like he belonged to begin with in the village. Page 2: when Hikaru asks Yoshiki why he wants to leave so badly, and queerness is indirectly brought up; it's clear Yoshiki feels like he can't exist within the village, implied to largely be due to him being gay. These parallel each other, suggesting Toshinori may also partially feel like he doesn't belong due to queerness.

Beyond both Yoshiki and Hikaru's personalities being similar to their fathers as a parallel, it is clear that Toshinori and Kouhei were very close, like what Yoshiki and Hikaru had. In fact, the flashback of their father talking together is in the same room that Yoshiki and Hikaru hang out in at the Indou's, around their same age (when the conversation could have occurred anywhere else), directly parallels Yoshiki and Hikaru. Even their conversation in that scene about the girl Kouhei likes is reminiscent of the dynamic Yoshiki talks about having with Hikaru when 'Hikaru' asks him what type of person he was, in that Hikaru would clearly talk about what crush he had--while Yoshiki wouldn't say anything about his own feelings, much like Toshinori also doesn't within the flashback, (and both to Tsujinaka's seem non-plussed about the topic). Their closeness is also shown by the amount of information Toshinori actually knows. He knows about the Indou's sin and the ritual; and the elders said that the ritual is something only known how to be performed by the Indou men... and yet Toshinori knew what it is, and knew who Hichi was. It's also clear they later had discussed it more at length too, as it's shown that they both had discussed and decided together (within the anime; the manga seems to suggest it was only Kouhei) that the ritual and the story about the sin was something that was to not be burdened onto the next generation. Not only did they decide that together, but Toshinori also knew that Kouhei had gotten into an argument with the elders about it; meaning he trusted Toshinori with his opinions, and controversial ones, up until he died. Toshinori also doesn't seem to be social at all, even with his family and wife; but in the flashback to the festival, you see him smile at Kouhei and immediately agree when he's asked to join Kouhei and some of the other guys for drinks, and Kouhei uses a nickname to refer to him- 'Toshi', rather then his last name, or just his full given name, indicating their closeness. Also, Toshinori's closeness to Kouhei is completely juxtaposed to the space between him and Yoshiki; they are both sitting far apart, and in the anime, they are even separated in some shots, indicating their estrangement even then, even if Toshinori is trying to connect with Yoshiki (also interesting that the memory stuck with Yoshiki- why?). Also, Kouhei's hat which seems to be strongly associated with Kouhei, is a hat for the sawmill; the same place Yoshiki's dad works for presumably, suggesting they may have worked together. Kouhei also wears orange, similar to the pants Toshinori wears (both are generally colour coordinated to orange- matching each other), although the clothes are slightly different. But it's clear they are some sort of canvas type work clothes, which suggests that he may have indeed worked there, although we know that one of Hikaru's grandfathers owns a shiitake farm.

First two images: Pages displaying Toshinori and Kouhei's interactions at the festival, both smiling and are very familiar with each other; directly after, Yoshiki compares the interaction to Toshinori and his mum fighting, showcasing the difference between the relationships. It is implied this stark contrast of relationship between them makes that memory stick in Yoshiki's mind; also, Kouhei is wearing the sawmill cap and uses a nickname for Toshinori. Third image: Mikasa mentioning that they don't know how to do the ritual, although they know of the sin of the Indou's; indicating that Toshinori knew a lot for someone who is not part of the Indou family.

Now the most obvious part of their closeness, and Toshinori's feelings, is how Toshinori says he felt that 'everything good in the village died that day' when Kouhei died. That is... a VERY strong comment, especially considering it's implied Toshinori's whole family, that his mum and dad are in the village as is any cousins or aunts, and most of all, that his wife and children are literally part of the village. One could suggest he is leaving them out of his statement, but that feels unwieldy, and it's obvious he struggles in his relationship with them as well; in a way it's clear he didn't with Kouhei. It is important to note he mentioned that he says it felt like (or in the manga panels below, thought that) implying those were his feelings and initial thoughts, but not nessicarily his actual beliefs. It's clear that Toshinori suspects that Kouhei was likely killed by the village elders after arguing with them about ending the ritual, which would certainly make one deeply loathe the village elders... but not nessicarily to the point that one would say nothing good is left in the village. Overall for Toshinori, it seems that Kouhei was the only person he really connected to (I would presume at one point his wife... but you really don't see that at all, and it's clear they've been fighting even when Yoshiki was younger, so it doesn't seem to been a happy marriage for at least a good number of years) and so when Kouhei died, he was devastated. This almost sole connection to Kouhei and his declaration about nothing good left in the village, including his family, suggests that just like Yoshiki with Hikaru, Toshinori had feelings for Kouhei and is also queer.

Toshinori talking about his suspicions and Kouhei's death; and answering in this translation that "I thought that now there ain't a single valuable thing left in this village anymore...' and Yoshiki thinking that 'he's so much like me, it hurts'; suggesting that Yoshiki felt similar knowing that Hikaru was dead, and suggesting they both felt similarly towards their respective Indou's in having sexual and romantic feelings, not just platonic feelings.

For Kouhei, it is harder to grasp his exact emotions for Toshinori (much like it is difficult to say with confidence exactly what Hikaru's emotions for Yoshiki was, beyond he loved him deeply), but you also see that he clearly trusted Toshinori and cared about him deeply. This is also displayed in that Yoshiki comments that the only person they could ask and who was close to Kouhei, was his dad--suggesting that Kouhei, although seeming to be cheerful and had got along with a lot people, wasn't actually close to many, if at all, beyond Toshinori. It does make one wonder about what Hikaru's mum knows, since it seems like she doesn't really know anything, and she would've been just as easy- or in fact easier (for Yoshiki) to ask. Whether Kouhei was queer however, much like Hikaru, is not easy to say definitively. At least with Hikaru, you get enough to see how he would make half-joking flirtatious comments to Yoshiki, comments that are mildly homophobic, but also almost probing to see Yoshiki's response to his flirtation; something someone closeted and unsure of a possible backlash of homophobia would make; unfortunately, with Kouhei we are given scant knowledge of their relationship and interactions, and as a result it's even more difficult to determine Kouhei's feelings towards Toshinori. However, what is clear is that both Kouhei and Hikaru were attracted to women, and seemingly outwardly content with the heteronormative expectations of them and generally either unwilling or unknowing in exploring beyond that. Nevertheless, it is also clear that they also both loved Toshinori/Yoshiki deeply, in a way that surpassed all their other relationships, and they may simply have been queer in terms of bisexuality or pansexuality.

Kouhei's enthusiasm about the girl he likes; in the anime this is clearly set in the same room as Hikaru and Yoshiki in the current day. Yoshiki mentioning that Hikaru had crushes. Both indicate that they experienced attaction towards women; but also clearly shows in their sharing that they were close to their respective Tsujinaka friends (and doesn't discount the possibility that they may also have returned their affections, but never acted on it).

And these parallels between the two different generations, provide a context of the expectations of the village and the village will do to keep their rules/traditions as enacted through Toshinori and Kouhei, that Yoshiki and Hikaru relationship develops under. With Toshinori and Kouhei, they both fulfilled the heteronormative expectations, marrying and having kids (while remaining close friends, but seemingly nothing more than that), and both of them knew of the Indou's sin and Kouhei took up doing the ritual. In this way, Toshinori and Kouhei represent what could have been Yoshiki and Hikaru's future, had they acted out social expectations (not that they would have particularly) and had not Hikaru died: potentially a unhappy marriage for Yoshiki, a close friendship that only remains a friendship, and both ultimately ending up chafing under the traditions. Although heteronormativity was achieved, it's also clear that by the time Hikaru and Yoshiki were little, that Kouhei is discontent with the expectations of the elders and the traditions, arguing with the elders about the ritual. We don't know exactly how Kouhei died, and whether or not it was foul play by the elders (and I'm very curious if we will ever get given the actual details, which I think we will-- there's a bunch of other past things attributed to the elders that is shady, which I'd love to learn more about), but the interpretation we are given from Toshinori is that the elders, in response to Kouhei questioning their traditions and wanting to not pass them to his kid and the next generation, had him killed, because the elders saw it as a threat to their safety. Kouhei's death narratively is an example, and a threat, of what happens when you go against what is socially expected of you within the village, and what happens when you break the traditions; keeping the traditions and ritual ongoing is prioritized over human lives due to the deep degree of fear associated with keeping the traditions (interestingly, mimicking the older form of ritual itself, which required human heads for blessings).

And this degree of severity of what the village will do when the traditions are trespassed, is something which could be also applied to how queerness is treated by the village just as readily as choosing to end the ritual itself-- with horror, as a threat to their 'safety'. We are given the knowledge that there was one other son within a family who was gay, which caused a huge fight within the family- so technically we know that it's unlikely the village would go to the extent of killing him in response to his queerness. However, it is clear that the whole manga closely corroberates queerness and monstrosity (stemming from the way that queerness is often construed as something monstrous, displayed by Yoshiki's own admission to being a monster as well) and so this threat of violence is also directly transferred to 'Hikaru'. This is plainly displayed in the newer chapters and what they've done to him by outing him violently--similar to the violence that occurs and can occur in response to forcibly outing queer folk. In this way in this scene and throughout the manga, the Ununki/Nonuki/'Hikaru' functions as a stand in for queerness, while the villages obsession and fears connected with continuing the ritual and passing down the story of the Indou's sin, functions as a stand in for queerphobia, and the violent actions that can be born out of the fears of queerphobia (amongst other things). Even the way that the Indou's sin and it's ritual was born from the shame and ostracization from the village which has been passed down (more specifically the elders in this case), it is similar to the way shame and ostracization is experienced by queer folks within a queerphobic culture.

Not only does the parallels between Hikaru and Yoshiki and their fathers both provides a foreshadowing of this danger, but it also displays the cycle of fear and violence perpetrated over generations when these ideas are continued to be passed along. When Kouhei and Toshinori decide that the ritual and the story of the sin should not be passed down, it is undoubtedly partially in response to the harm done in the name of fear within the village as a result. The harm perpetrated includes that of the shame felt by the Indou family, who are clearly ostracized by the elders and distrusted because of the fear surrounding the ritual and the Indou family. And this fear and harm perpetrated as a result is tangible when the village elders (supposedly) kill Kouhei in response to wanting to end the ritual. Not only is that strong display of what the villagers will do out of fear, but also sets the stage for another tragedy, and display of the dangers of the ritual; Hikaru dying, trying to do the ritual. Something that only occurred due to Kouhei's early death, who died as a result of his attempt to abolish the ritual- and something he expressly didn't want Hikaru to have to do. This harm that both Hikaru and Kouhei experience over the generations can be again mapped onto queerphobia, and what can occur when these predjudices are passed down. As well, in much the same way as queerphobia, the abolishment of ritual and the shame around the 'sin', both profits the villagers and the Indou family- the villagers fear no longer drives them, and the Indou's no longer have to shoulder shame and be ostracized and judged by the village.

Also; both Kouhei and Hikaru's tragic deaths as the result of the ritual leaves Toshinori and Yoshiki to both grieve them- another parallel between the two relationships.

Kouhei very plainly mentioning that the Indou family is hated.