MELTY BLOOD ORIGINAL TIMELINE
This timeline does not include Gag Routes or Melty Blood X. A Compilation including those will be created at a later date.
You might think the timeline is as simple as the chronological order the series of games came out, although you are correct you're missing one thing. In the Original Melty Blood game there are different Endings/Route which depend on the outcome of battle (as shown in the MELTY BLOOD GUIDE BOOK)
Now begs the question: "Which Routes are canon in each game?"
The answer is this:
MELTY BLOOD [Route K (Hologram Summer, King of Lies) + Route L (King of Lies) -> Route O1 (The Greatest Enemy) + Route O2 (The Greatest Enemy. True) -> Re-ACT Tohno Shiki Route/Sion Route -> Act Cadenza (there is nothing here, it just happens) -> ACTRESS AGAIN Tohno Shiki Route/Riesbyfe Route/Sion Route/Satsuki Route.
Now, it depends if you want to consider Satsuki's Status.
If she is deceased then from Re-ACT it would follow Sion's route and Actress Again it would follow Riesbyfe's/Tohno Shiki's.
If she is alive then from Re-ACT it would follow Tohno Shiki's route and from Actress Again it would follow Sion's/Satsuki's routes.
Now how is this all canon/true?
Well, the MELTY BLOOD Mangas cover Route K/L (it mixes Arcuied saving Sion & Shiki with the crimson moon and Sion fighting Wallachia Arcueid) while MELTY BLOOD: ACT 2 Manga covers Route O1/O2 (TATARI takes control of Kohaku who is defeated by Miyako since TATARI transferred into Miyako last minute and Arcuied crushes the remnants of TATARI
Its a bit obvious at this point. The true routes would follow our protagonists, Sion and Shiki but it can't be both. This part is up to your choice(ish) but your choice decides Satsuki's Fate.
Melty Blood is based on "What if Satsuki Yumizuka was alive" also known as the Satsuki Normal Route ending BUT there is a possibility where Melty Blood happens without Satsuki thanks to the Manga adaption. In the Melty Blood manga, TATARI creates the nightmare of Satsuki is actually alive. This is Shiki's Nightmare which comes to life since he could not save Satsuki.
So if you want Satsuki to live then you go down the Satsuki Route or Sion Route of Re-ACT. In Sion's route, Sion is stopped middway but Satsuki who wants to help on behalf of Shiki to stop Sion and let Len deal with White Len herself. Satsuki is defeated with no hesitation and Sion moves on to save the day.
In Shiki's route, Satsuki simply is not mentioned nor does she appears at all.
I can not stress enough about Act Cadenza, as its just a bunch of random happenings that relate to TATARI. It is unknown which one is true or not because they made the Arcade mode as if they just wanted to make random stories for everyone. Think of it like Type Lumina's story mode where it makes absolutely no sense when, where and what is the plot.
The only true thing that happened was White Len acquiring Nanaya Shiki as a Master or Familiar. They are both Master and Familiar to each other.
Last but definitely not Least is the final addition to the fighting game's original timeline but not franchise,
Once again here, the choice of which route you would want to take is based on Satsuki's Fate. According to the Actress Again PS2 Manual, the canon routes are said to be Tohno Shiki, Riesbyfe, Sion and Satsuki.
Just like Re-ACT, if you want Satsuki to be alive you choose Sion's route or Satsuki's. If not, you choose Shiki's or Riesbyfe but I do want to expand on this one a bit more.
Satsuki does not appear or is not mentioned directly in Sion's route for Actress Again, but in the ending of Sion's Route Riesbyfe is taken under Sion's wing since none of them can really go back to Atlas or the Holy Church. So the only place they can go is the Back Alley with Satsuki. All three of them forming the Back Alley Alliance.
You can see this clearly happening at the end if Satsuki's route where Satsuki comes home with Riesbyfe and all of them live together and the Back Alley Alliance grows with two more members (they included Roa since Satsuki met him midway to Osiris)
NOW, we return to the time where Satsuki does not exist.
In Tohno Shiki's route, Shiki almost looses all of his memories, makes it to Osiris and defeats her. Sion is only a bit sad she couldn't defeat Shiki but also that Shiki had to see what possibly could've been her if she went down that path (but she does not regret that he had to see it. In fact she asks Shiki to remember it and after arguing again Sion threatens to shoot Shiki once again silently)
Then there is Riesbyfe.
There's no way she could be alive right? Wrong.
The reason why Riesbyfe is alive is because she was consumed by TATARI but could never be broken down by it because of her conceptual weapon, Gamaliel. Riesbyfe's Holy shield deflects all impurities and magecraft, as well as keeps the user from ageing (As said by Riesbyfe herself in her win quote)
This is why, not only has Riesbyfe not aged one bit, but she survived being swallowed by TATARI itself.
But wait a minute, TATARI was destroyed right? It was yes, but this is TATARI, a Reality Marble, in the hands of Osiris, Sion's Future Self which had taken physical form since this form was parts of remnants of Sion's soul lost in TATARI itself as well.
As you've seen before hand in Re-ACT or even in Melty Blood itself, TATARI can somehow spilt and posses other people as it's host despite it being a Reality Marble or a Phenomenon.
Now in Riesbyfe's Route, Riesbyfe sets out to and defeats Osiris (pretty simple, but I'm skipping the details of who she meets and what she thinks because it doesn't have to do with much of anything but herself.). Now you might not think of this part but isn't Riesbyfe supposed to protect Sion? Yes she is, and that;s exactly what she's doing. You see, Riesbyfe is still sticking to the oath that she made with Sion. Osiris, the future self of Sion, is dooming the whole world, which includes Present Sion. In this case, slaying Osiris would mean protecting Sion. Simple right?
After defeating Osiris though, Riesbyfe disappers since she was only kept alive by TATARI. So after defeating Osiris, protecting everyone, including Sion, she returns to a deep sleep where she would possibly never wake up again.
With that, Melty Blood comes to an end. The era of TATARI finally closes and our Actors all move on with their lives.
But if you want more Melty Blood Content, and more with the Back Alley Alliance (without White Len and Roa) you should check our Melty Blood X and Back Alley Nightmare, which are mangas that come all after Actress Again. Which are all fun reads.
