As I was looking for spoilers for this show, I found a reddit user - SAMPTRA WRITER - talking about it, so I will copy their response to other reddit user.
Book 1:
''So Kan (Dr although in the book they call him Gun), was Wasan's mother's doctor, and she told Kan to look after Wasan. He said he would, but not with the intention to follow through but when he met Wasan he felt the electricity and they pretty much became fwb right away. As more people die, all signs point to Kan. They even find evidence, Wasan actually sends out men to follow him, puts trackers in his car etc. he believes he's guilty. But Kan knows he's being framed, and at this point is actually in love with Wasan and is trying to clear his name. He finds out he's being framed by his mentor doctor and confronts him Wasan follows him and it all comes out he's being framed the mentor tries to shoot Wasan but Kan jumps in front is is hurt. The mentor doc is shot and sent to hospital. So it's all wrapping up it was the mentor that was killing them framing Kan BUT major twist...the book ends with Kan disgusing himself, going into the hopstial and kills his mentor before he can testify becuase....Kan is actually the White Angel of Death and has been killing terminal paitents as per their request.
End of book 1.
Book 2:
So you book 2 starts with Kan and Wasan living together, all I well. Kan is still killing terminal patients that ask for it, and he’s starting to feel guilty keeping it from him. But then he gets a letter saying ‘I know you’re the angel of death’ and starts to panic. He almost kills a mentally ill man because he saw him in book 1 but at the last minute panics. The next patient he goes to euthanize is already brutally murdered. Desperately trying to solve who is murdering people he starts drugging Wasan so he sleeps and he doesn’t know he’s gone and he just digs himself deeper and deeper lieing to Wasan and eventually it all unravels and he’s outted as the Angel of Death, Wasan arrested him and he’s charged with the murder of his mentor from book one. It’s pretty brutal he confesses to Wasan about euthanizimg his mother and is sent to jail for murder. There is an 8 year timeskip, and Wasan who hasn’t spoken to Kan that entire time ends up picking him up and honestly bizarrely forgives him and they get back together….so happy ending Kan is on longer a doctors planning to open a cafe end….BUT small stinger, Kan gets an email asking him for help ending his life. Shocked Kan shows Wasan and the cop says ‘aren’t you going to help him?’ And end
I left out the side plots but the main narrative is here, it’s arguably one of Sammon’s better books.''
