Ein magisches Gadget von Lala verwandelt Rito in eine putzige Maus und eröffnet ihm damit ganz neue Perspektiven.
Rito finds Momo in his bed again. Momo reminds Rito about her harem plan and advises him to be careful of Mea. Meanwhile, Mea is worried that Nemesis is not responding to her. She tries to hide her feelings from Nana who is inviting her to a bakery. Elsewhere, Tearju thanks Rito for helping her and asks him if Momo has new information about Mea. Momo is more concerned about Yami skipping classes. Tearju understands Yami's motives about staying away from her and wishes to see her in school and Mikan, Yami's friend. As Rito thinks about the friendship, Lala bumps into him and accidentally drops an invention. Rito activates it turning him into a mouse. Being small, Rito can easily see girl's underwear, making him uncomfortable. He desperately searches for Lala but his small size makes him vulnerable to being stepped on. His escape attempts eventually lands him under Yami's clothing. Rito manages to escape with her underwear but passes out. Mea finds Rito and remembers Nemesis message about weak people being weeded out. She helps Rito anyways and Rito recovers in time for a beating from Yami. As Yami walks off, Mea asks Yami about feelings and how Nemesis has never taught her this subject. Yami tells Mea that she should discover it herself. Afterschool, Rito finds Mea on the roof in her battle clothes and asks about her motives. He tries to convince Mea not to rely only on her master Nemesis but it enrages her. Mea seduces Rito with her Psycho Dive ability, but alien enemies also approach and attack Mea, leading Rito and Mea on a wild rampage. During the fight, Mea realizes that Nemesis is reminding her that she is a weapon. Nana also spots Mea in her weapon form.
Au lycée, Rito ramasse une invention qu’a fait tomber Lala et se retrouve accidentellement transformé en souris. Il se met à la recherche de la princesse de Deviluke afin qu’elle lui rende son apparence normale, mais sa nouvelle forme va lui compliquer la tâche et lui causer bien des misères…
ある日、リトは学校でララが落とした発明品を拾う。メカは手の中で作動して、リトは小さなネズミの姿に変身してしまった！ 助けを求めて校内をさまよう小ネズミ・リトだったが、沙姫や春菜、唯、ヤミなどを相手に、次々と〝とらぶる〟を巻き起こすことになってしまう…。やがて力尽きたリトを助けたのは、マスター・ネメシスとコンタクトが取れず、不安な日々が続いていた芽亜だった。
벌써 2주이상 연락을 해오지 않는 마스터에 불안감을 느끼는 메아. 한편 또다시 라라의 발명품을 섣불리 건드린 리토는 쥐로 변하고 마는데...
Rito encuentra a Momo en su cama nuevamente. Momo le recuerda a Rito sobre su plan de harén y le aconseja que tenga cuidado con Mea. Mientras tanto, a Mea le preocupa que Némesis no le esté respondiendo. Intenta ocultar sus sentimientos a Nana, que la invita a una panadería. En otra parte, Tearju agradece a Rito por ayudarla y le pregunta si Momo tiene nueva información sobre Mea. Momo está más preocupada porque Yami se salte las clases. Tearju comprende los motivos de Yami para mantenerse alejado de ella y desea verla en la escuela y a Mikan, la amiga de Yami. Mientras Rito piensa en la amistad, Lala se encuentra con él y accidentalmente deja caer un invento. Rito lo activa convirtiéndolo en un ratón.
