Takeshi and Michi stay overnight at their school to study, where Takeshi picks up a card and Michi tells him that it comes from a game called Weiß Schwarz and that she has won many tournaments involving that game. Michi ends up getting sucked into a portal.

Takeshi enters the portal that Michi was sucked in and encounters the VS Ji-san. The VS Ji-san tells him he is in the Weiß Schwarz battle space and that he is the chosen warrior. Suddenly, a giant card battlefield appears with Michi standing on the other side, and Takeshi is told that in order for him and Michi to leave, he must become stronger by playing the game.

Takeshi is given a deck to use against Michi, which VS Ji-san calls the "Great Galaxy Deck", or "GG Deck" for short. Takeshi ends up losing.

Takeshi continues his training, but still ends up losing every time.

Takeshi, Michi and the VS Ji-san encounter new opponents.

Takeshi fights the three chaos sisters - Sies, Operetta and Cal. Takeshi manages to use a kick to peep under their clothing.

Takeshi is down to level 3, but uses three cards to attack the girls. One of them contains Yu Narukami from Persona 4.

The three chaos sisters are finally defeated.

Two new opponents appear in the third door, but they won't fight if there are girls around.

Joe starts by summoning a weird monster, but the fight is interrupted when Michi leaves Takashi's pocket.

The fight between Takashi and Joe continues.

Coud takes over the fight, but is defeated.

Takashi prepares for battle against Michi, his final opponent.

The fight begins, but Takashi refuses to give up.

Takashi promises to take Michi back with him if he wins and uses Climatic Countdown.

Takashi and Michi are sent back to their own world, but Michi does not remember anything that happened there.