I thought he has a twin brother or something
i mean tht could be it to but it just seemed like he was another person in the same body
It is multiple personality disorder. There is another story I know of where the Seme has multiple personality disorder. http://www.mangago.zone/read-manga/koibito_no_namae/
There is another one where there are three, and two of them are uke. http://www.mangago.zone/read-manga/nounai_ren_ai_no_susume/
Seme with 4? different personalities
http://www.mangago.zone/read-manga/kokoro_logic/mf/v01/c001/
I read a few more but I can't think of them
omg a manga where the seme has multiple personality disorder .. its something new and im loving it