Been thinking about Kotoyuki's limerance
The fact is we can find some letter showing a young Kotoyuki who doesn't understand why he must go through all this and can't be like other children, which made him resent his situation and be in a mindest of "when I am grown up, I'll do whatever I want, I'll have whatever I want"
And despite having never got the chance to be a child, I think this childish mindest explains and even fuels his limerance for Hinako
As he explains that his time with playing with the other kids was very limited, this means his relationship with Hinako meant even more to him than I'd initially believe, she basically offered him moments where he could be himself : just a child, not a perfect heir. And so, when he began to have feelings for her, this childish "I will have whatever I want once I am grown up" was transfered to his desire for Hinako
When we read his letters and how he is incredibly focused on his own feelings rather than talking about the girl he cares about, this reads as very child throwing a tantrum. And this tie into the idea of love as being an egoistic narcisstic feeling where one isn't yet capable of loving the other and is too focused on their own feelings.
For comparison, in Romeo and Juliet, Romeo starts off as having feelings for Rosaline and the way he talks about her is very similar as he only focuses on his feelings and frustration to not have her, commentators often points to this idea of childishness and egoism, and I think that's the best way to describe how Kotoyuki comes off in these letters
This could be an interpretation of the "curse" or "spell" he is under : wanting to heal his frustration as a child that he couldn't simply be a regular child and had to be perfect because of his mother. This would fuel his desire to have Hinako, moreover, since he can do what he wants when he is with her, this could also explain why he desired her so much
This makes his desire to be a perfect husband even worse as the thing he didn't like, he motivated himself by making Hinako his main motivation but in the ending where they actually get married, neither she nor he can behave like how they want to : Hinako ceases to be the girl he fell in love with and he can't be the person he wanted to be, a simple person who was enjoying his time with Hinako when on the playground
This also makes his adult appearance contrast even more as a facade considering that deep down, he didn't really grew up but was forced to. Obligatory Umineko comparison, but this reminds me of Rosa claiming to have grown into a splendid adult only for her to be a 14 year old stuck in a 33 year old body or so, and in this aspect, this makes Kotoyuki foils Hinako in an interesting way
Hinako is torn between her past and her future, Kotoyuki has only lived in the future, Hinako clings unto her younger selves but feels torn between her young and older self while Kotoyuki appears as his adult self because he never got to be a child but deep down, he is still a child and didn't really grew up
And honestly, what makes the true ending so poetic is that not only did he finally got to taste the treat he couldn't eat as a kid, but that's how you realize that's WHY he fell in love with Hinako : because of her unruly side and because with her, he could just be an average kid, and by helping him, Hinako gives him a chance to make up for that
