so busy I forgot abt this

So I finding this yaoi abt a guy uke is an agent? That is investigating abt serial killer killing ppl but then when they met uke and seme uke begs the seme to kill him cuz he never dies the seme fck and kill him every time? The last chap I read is their at train the uke is being hunted by some agents? Cuz they found out his immortality and take note this happened like Victoria era? Something like that