Ralen said: I'm not that familiar with this character, so I don't know if he's referring to his actual sister, or just older women in general.
He's a time traveler, from a group of such that actually wish time travel to never be invented because its existence runs contrary to the idea of free will. From what I've read, he is actually the younger brother of Mikuru, but from a timeline that has been effectively negated by time travel so Mikuru doesn't know him as he was never born from her perspective.
*pet*I would do anything for herYou're a good boyAnd then, yesterday, when I was helping......I wish*pet*Koijumi-kun said I was a good girl, and patted me on the head♥My big sister would pat me on the head...Are you a good boy who helps out?GrrrA man who really tried to do anything for his sister*bluuuush*