Yûta Kobayashi is a Japanese fifth-grader living with his parents and younger sister, Akane. He owns a Famicom (NES outside Japan) and a copy of Mega Man 5. One night, playing late, he forgets to turn off the console before sleeping. This act allows Mega Man, Dr. Wily, and other game characters to enter the real world.

Yûta partners with Mega Man to thwart Dr. Wily's plans for real-world conquest. He joins missions, offers strategic support, and helps navigate real-world locations like Tokyo. He aids the search for Wily's base at Mount Fuji, skipping judo practice to summon Eddie for crucial energy replenishment. Later, he assists Akane in summoning Proto Man and Beat to fight Wily's lava robots near the volcano.

Yûta acts as a cultural guide for Mega Man and Roll, explaining Japanese traditions and daily life. He participates in and describes New Year celebrations with otoshidama, Setsubun bean-throwing to ward off oni, Hinamatsuri (Girls' Day), Children's Day with koinobori streamers, and Tanabata. He also details Japanese geography, bullet trains, and educational practices like cram schools.

His family interactions include typical sibling arguments with Akane over the video game. His parents react with surprise and varying acceptance to the extraordinary events; Mr. Kobayashi even drives Mega Man to Tokyo. Yûta demonstrates responsibility and growth, prioritizing the missions over leisure activities and showing increased awareness of his actions' consequences.