Boku

Rin's big brother in a post-apocalyptic future where human have evolved differently and where they were annihilated by their "creations". He has taken care of his little sister alone since their mother abandoned them so that they could survive because they represent the last hope of humanity.

They live alone in Sakurano, devastated by the war, where they hide. His favorite hobby is reading and writing fantasy stories that end well, where everyone is happy and he teaches his sister the pleasure of reading stories.

However, their peaceful life is interrupted one day. The machines found them and they are forced to flee.

"Nii-san" is heavily injured during his fights to protect his sister and at the end of these, after having secured her, he begins to die peacefully...

Before giving his last breath, he attends to the miracle awaited by all humanity. The sadness and pain of losing her brother awakens Rin's power and she creates a new temporality where her brother would finally find happiness.

He is currently reincarnated in the person of Yuuma.