Yōichi is attached to Natsume, but seems to dislike Mikan at first. Later, he becomes attached to Mikan and even kissed her on her cheek once, and he became very fond of Mr. Bear. He eventually starts to "cling" to her later on in the manga.
He has the Alice of summoning bad spirits, a Dangerous Ability type. He is very bright for a three year old. Natsume likes him since he feels that the boy is just like him and Natsume is also helping Yōichi to be transferred out of the Dangerous Ability class.
Like Mikan, he loves "Fluff Puffs," (Howalon in Japanese) the best selling candy in Central Town.
During the Hana Princess arc, he accidentally ate an aging candy that he stole from Hotaru which let him gain an ability that turns him into a 13-year-old. The side effects gave him the ability to switch between younger and older self. He still has the mind of a three-year-old when he changes his age, which makes it awkward for Mikan in some situations, because he likes hugging and carrying her. He even develops a huge crush on hotaru.
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