Oh ho ho. This could be interesting. Rokudou has done some neat reversals of tropes or busting away from certain fallbacks so Yagen's monologue at the end there could be moving into a really interesting place of either society dictating how a man should act or what is considered proper behavior for a man or into gender issues.
I won't use the word that specifically refers to this problem because God knows some people would REEEE themselves into a coma or bust a blood vessel.
@OniBarubary Trans. Just say it. Piss on the comment section retards. Yagen might be trans. However, it's way more likely he just doesn't want to be pigeonholed as a "man amongst men" leader type and just wanted to make a clean break with the past before he somehow got tangled up in Chromosome. He probably just doesn't want his worth as a person to be defined by his status as a fighter or leader of men and wants to make his own way forward.