Scenario

An Breed/MHA/BNHA AU

Inspired by Higuchimon's Breed AU and MHA/BNHA

Overview: 

Yamato and Taichi are already dating and arguing like an old married couple. Taichi was pulled through an distortion and Yamato went after him. When Yamato went through the distortion, his dark side (Yami or Akira, known as the dark prince of digital world) took control who enjoys chaos, taking over the world, and messing/making Taichi more complaint as in Taichi can't do much against as long as Yami/Akira is in control and threatens to hurt those he care about but he is the only one who can bring Yamato back to his true self. Yami/Akira enjoys flirting with Taichi as well as taming Taichi's fire/will to make Taichi his. 

There are slight differences between Yamato and his darker self such as Yami/Akira (dark Yamato) has red eyes when in the dark and his hair isn't as blonde/golden. It could have either black highlights or is a dirty blonde when there is sunlight reflected on it when there is no light then it looks normal to an extend it is not as blonde.

Taichi realizes that dark Yamato is in control and be like:

Yami/Akira: I missed you Taichi, it been too long or has it, really depends. Didn't you miss me.

Taichi: like I miss a royal pain. Give Yamato back control.

Yami/Akira: no, I don't think I will.

In this AU, it is like MHA/BNHA where there are those born with power and those who are not. Yamato dark side has the power to knock people out with a mist ball and create things while Yamato control ice and create things with ice. Taichi can control fire. Both are fighters but Yamato is slightly stronger than Taichi. Yami/Akira is stronger than both of them. Taichi is good with surprise attack.