So ryo is canonically bisexual :0?
well, Anon, I think so due to the fact in Violence Jack Ryo fell in love with Miki and he is always in love with Akira in the manga, manga spin offs and every anime adaption.
But its not outright stated at times, and Go Nagai never has him say he is bisexual or gay, just that he is in love with Akira. And some writers do have Ryo be gay or at least only romantically interested in Akira, for example in Shin Devilman written by Hiroshi Nagai who is Go Nagai's older brother and Go Nagai ofc Illustrated it
and yet in Violence Jack by Go Nagai, Ryo is in love with Miki.
and in Devilman Saga Ryo seems to state that him being intersex informs his bisexuality? I'm not sure but this is what his speak sounds like to me, even if its really messy af
So yeah, unless Go Nagai says one way or the other I would say that all we we know for sure is that Ryo/Satan is Queer af and I don't think its wrong to headcanon him as gay, bisexual, pansexual or demisexual since Akira is the only one he loves and he was friends with him first. The point of him possibly being demisexual could explain why Ryo falls in love with Miki in Violence Jack since he actually got to know her this time round.
But again I don't know how Go Nagai envisioned Ryo's sexuality and he isn't really talking about it either so all we can do is decide for ourselves what to headcanon.