The supporting character's harem is very normal - Chapter 393 What if I can do it?

Nijigen is a freshman and Banri’s friend. He gains his nickname at the tea ceremony club’s welcoming party after declaring his despair of the three-dimensional world and that he would live for the two-dimensional world from then on. His nickname in high school was “Satoutaka”.

Hello, welcome to join the scp foundation, as a D-level personnel, you will get the following benefits:

First, you will get a unique identification number printed on your brand new orange clothes (prison uniform), such as D-213.

That’s not enough, you will also get a brand new name, which you will use to communicate with each other in the future! Like Billy-D.

As a D-Class, you just have to satisfy your superiors, and they’re good guys with guns! They will help you to have friendly interactions with all kinds of safe creatures (help the ten-meter killer lizard clean the room)

In order to protect your health at all times, our infirmary is always open, even if your work here is as easy as taking a walk!

When you’re done with a D-Class for a month, you can go home (and be shot), no matter what prisoner you were-

Don’t wait any longer, come and join scp!

- Description from novelbuddy

In a world dotted with World Entrances to a demon world, demons have invaded humans for centuries. Humanity has united and one of the most ancient sects in the world, the Archean Mountain Sect, has set up an entire education system in the form of Dao Academies and defenses at the World Entrances.