Mirai

MIRAI, also referred to as Future-kun (フューチャーくん) by Teppei Sasaki, is a toy robot that Okano gifted to Teppei during their graduation. After the lightning bolt struck Teppei's microwave and turned it into a time machine, Mirai's bottom half was subsequently melted.

Appearance
Mirai is a light blue-gray colored toy robot, with round eyes that glow a green color, and a rectangular face, body, and mouth. On its chest, the word 'MIRAI' is written in blocky yellow letters. Mirai also has a long antenna jutting out on the top of its head.

Due to being placed on top of Teppei's microwave, Mirai's lower half was eventually melted away after the microwave got struck by lightning. Afterward, it could occasionally be seen emitting sparks.

Synopsis
Mirai is revealed to be the reason behind the time travel, feeling a complusion to save Aino. He's been using his powers to create a time loop, trying various ways to prevent his death.

Trivia

 * Mirai seems to be self-aware that he is in a manga, saying "I'm nothing more than a neccesary character in another author's story."