Klavier Gavin
So this is a little headcanon about Klavier Gavin.
SPOILER WARNING
There WILL be spoilers to Apollo Justice:Ace Attorney and Danganronpa:Another Episode in this.Do not read if you have NOT finished either games!
In the 4th case of AJ:AA,Kristoph Gavin is found guilty of killing Drew Misham.He also requested a forgery that Phoenix Wright presented in court in his final trial until Dual Destinies.Now,the prosecutor in this case,Turnabout Succession,is Klavier Gavin,Kristoph's younger brother.
Now,we can see glimpses of how Klavier feels about Kristoph's arrest,but we never see it fully.So I have a theory.Klavier feels broken inside after Kristoph's execution and ventures to Germany until Dual Destinies.Meanwhile,Apollo tries to contact him,telling him any news about Kristoph.But Klavier never responds.Why?Because the only family he had is dead.
Now,it's only a possibility that Kristoph was the only family Klavier had left.It may be possible that his parents are still alive,but for the sake of the headcanon,let's say they aren't.
Flash back to when Klavier is in his mid teens,most likely around 14 or 15.After the death of his and Klavier's parents,Kristoph begins to feel hatred boiling up.He starts treating Klavier like litter on the side of the road.He starts treating Klavier like how Masaru Daimon's father treated him,minus the buying alcohol and cigarettes for him.
Klavier is forced to work as hard as he can,to be everything their parents wanted them to be.Every day,he comes home from something,and Kristoph is there,expecting Klavier to work harder than he did the previous day.
I guess this behavior is more like Nagisa Shingetsu,but Masaru seems even more like Klavier after you've read Masaru's memoir.Here's an example of what is written in the memoir:
"I'm sorry,I'm sorry.I'm sorry."
The words "I'm sorry" are repeated in the first sentences of the memoir.Now,back to Klavier and Kristoph.Every time Klavier messes up,Kristoph punishes him in some way.Klavier repeatedly tells him "I'm sorry",but to no avail.Eventually,Klavier fights back,placing that scar upon Kristoph's right hand.Kristoph knows Klavier isn't messing around,but takes it the wrong way.He thinks that Klavier is tough enough to withstand the work and training Kristoph puts him through.
But Klavier wasn't.He was afraid,afraid to come back home and face his brother with the training.But despite all that,he still loves Kristoph.
And when Kristoph leaves for good,Klavier is heartbroken.