Damn, the author must really hate Solso for him to get this kind of treatment the whole series. I already complaining about how little screen time Solso got since early chapter, but this is wild.
Ever since he first introduce, he keep getting pushed out from almost every fight in favor of Yuri or other stronger character to show off. It also doesn't help that author keep introducing this stronger hunter number 1,2,3 in short amount of time, making him even more forgotten.
They give him this interesting backstory but never explore further into it or give it a fair conclusion. When he found out his brother turned into chimera, all done in one page without any dialogue then they kick him out from the rest of the story just like that. Meanwhile the other character got a whole chapter of their happy reunion and celebration.
They could just take him out from the story and get the mask guy to do the whole kidnapping Yuri part and nothing will change. Well, at least the manga already finish now.