I don't understand the first story, but I really want to:
"Hard Triangle- Mutiple personalities, murder, rape and a shady past between a doctor and his teenage patient."
Please share your interpretations. So what was the ending? I didn't get it completely. I feel like the story totally didn't finish. . .

"No one has ever written, painted, sculpted, modelled, built, or invented except literally to get out of hell."
~ Antonin Artaud

It's not that hard to understand. Minami Megumu always has an interest in exploring Christian themes and sometimes she plays by twisting it around.

Hard triangle -> trinity -> the trinity is God that exists as three persons: God the Father, God the Son, and God the Holy Spirit.

The story -- heavy spoilers

Rei/Kei thought the doctor was a gentle person who could save him, but he couldn't forgive him for leaving him, making him a target of the sexual abuse. He wanted to mess with the doctor as revenge. He also believed the doctor felt guilty for what happened to Kei so he took advantage of it as a means of being saved.

He also believed the person who "trained" him to become the "2nd" serial killer was the doctor's father, the original serial killer who later committed suicide, but the truth is, as he found out in the end, it was the doctor all along. He was the rapist, the original serial killer and the one who taught Rei (through Kei) to kill.

When Rei realized that truth, he quickly realized he'll never be saved because he's trapped in a new cycle of abuse. The doctor isn't an angel after all because he turns out to be just as evil as their fathers and himself.

It's not one of Minami's best works.

wow, i dont get that at all lol