I wonder how many different alters he has. I would be surprised if he only has one tho since that very rare and somewhat unrealistic....BUT hey it's yaoi and rarely is mental disorders probably seen in movies, mangas and etc.
Not everyone with DID is Billy Milligan.. having just one is common with DID cases and even that is quite hard.
People have DID only after experiencing massive trauma in childhood such as intense abuse for excessive period when child creates alternative persona as way to deal with it and “protect themselves”.. so even one alter persona is bad enough..
I am curious if author had enough knowledge about DID, and if they did, how will they tackle it
The Guy who the Uke admires is gonna be the Seme or related to the Seme in some way...tbh ive seen this trope too many times that I began to expect it ┑( ̄Д  ̄)┍
Might also pop up as a love rival.