straight seme x straight uke
uke fall in love first.
Both seme and uke are straight.
straight seme and uke also straight but is the type to be "gay for the one they love?", meaning that he will only be gay for that one person.
uke fall in love first.
Straight x either straight or bi
Both straight.
Seme fall in love first.
Both straight.
unknown preference x straight
straight, gay
both of them are unknown sexuality/preference. One is a scientist very curious of everything. The other is, romance is not in their book, has no interest with human or anything other than doing his job.
Koi wa Nanairo Shichihenge!?