The Fourth Year After My Secret Crush Died

I'm an investigator of mysterious incidents. I once had a partner, codename Mountain Bird. He had a highly deceptive face, but he was rotten to the core. I liked him a little, and suspected he might like me, too. But before anything could happen between us, Mountain Bird died. Four years after his death, I met someone who looked exactly like him. His face, voice, personality, memories: he had everything Mountain Bird had, and more. For example, translucent limbs like the tentacles of sea creatures, which appear when he's worked up and flail wildly at everything around him. On top of that, we were trapped in the same eerie mansion. Filthy whispers that seep straight into your brain, monsters that used to be human, humans in monster disguise... Behind every door, a fresh surprise awaited me. But it's completely fine. I'm a veteran investigator. Every morning when I open my eyes, I feel refreshed and full of energy. As for the strange things behind the doors always disappearing when "Mountain Bird" appears behind me, and the way I seem to be tightly embraced by a hundred arms at night, those are all unimportant details. Today, all four of my limbs are intact, and I'm in good spirits. So is he. * The main story is written in third person. * Not orthodox Lovecraftian horror, not a tabletop role-playing game. The atmosphere is probably more COJ (looking away). Strong leads. At heart, it's a love story. * Also known as "Mixture": "At what point does the proportion of inhuman things in my body mean I'm no longer 'me' to you, but merely a familiar-looking mixture?" * I really want to write this story, but I need to practice writing plot first. Blurb written on 2023.04.07-08 Theme: Strive to be a normal person