Is there a love triangle in this one?

No

kind of...

spoilers:


just that the odd point of this obtuse triangle is the bad guy (who's a psycho) that developed an obsession with the uke (cause he's a psycho, lol) who was in love with his true seme and ML

so the triangle isn't one where the 2nd ML is an actual contender for the uke's love but rather he's just obsessed with him and holds one-sided feelings and ulterior intentions

to the point where he killed the uke in his past life...