Monika

Monika is the president of the literature club at her school and the first non-OC or super sentai or power rangers or Kamen rider character to appear in the Kuroninja Multiverse. She was Kuroninja’s Earth-0 Counterpart’s girlfriend in this timeline until he left her for someone named Kurumi.

History
It all started when Kuroninja’s Earth-0 Counterpart played this game called Doki Doki Literature Club. It was a dating simulator, but you can‘t date Monika in this game. Because of this, Kuroninja’s Earth-0 Counterpart decided to go for the one with the knives, but then something known as Act 3 happened.

Instead of deleting Monika like in all the other timelines, Kuroninja’s Earth-0 Counterpart invited her to the Kuroninja Multiverse, due to the fact that Kuroninja’s Earth-0 Counterpart also felt lonely, which is probably the reason why he bought the game in the first place. What a loser. Unfortunately, due to the fact that the multiverse’s fabric isn’t used to crossing over, it resulted in Venom symbiote ripoffs invading Earth-1. Kuroninja and the RMS teamed up with Monika to stop them, and Kuroninja handed over his Koto Kyutama over to Monika. Monika then became the M of RMS, replacing Kuroninja.

Later, Kuroninja’s Earth-0 Counterpart realized that Monika had the power to Cross Over, which meant that he could expand to other universes that aren’t Toku. Kuroninja’s Earth-0 counterpart used this power to add the rest of the DDLCverse to his Multiverse.

Kuroninja 0's betrayal
After the events of Kuroninja Gold, Kuroninja's Earth-0 Counterpart left Monika for someone named Kurumi. Monika didn't take it very lightly and began seeking out the 5 Dragon Orbs. She found the White Dragon Orb and gave it to someone from Earth 46. When he failed, she became the White Dragon Warrior herself.

Kamen Rider Decade
After a long absence in almost the entirety of 2020, Monika returned in Kuroninja's 5th Anniversary Special, this time, with Kamen Rider Decade's powers. Monika had returned to either destroy the Kuroninja Multiverse or stop Kuroninja of Earth 0 from ruining the anniversary special with his waifus. Monika also removed all the Metal Heroes characters from the special.

Trivia

 * Monika is not evil in this timeline, or at least, she didn't start as evil.
 * Monika is the first ever non-toku character to appear in the Kuroninja Multiverse and not be an OC.
 * Shes only in the Kuroninja Multiverse because Kuroninja’s Earth-0 Counterpart is a DDLC fan and saw how popular it is, even after months and months.
 * Monika is the only member of the club who didn't train in the Kuroninja Dojo.
 * Monika has had the least appearance compared to any other DDLC character who showed up in the Kuroninja Multiverse. Here's a list of her appearances.