|Japanese Name||音無 伊御|
|Romanized Name||Otonashi Io|
|English Name||Io Otonashi|
Io has dark hair and an ahoge. He has black eyes, and wears glasses due to his nearsightedness, and is practically blind without his glasses, since he had trouble recognizing Sakaki at close range without them.
He is intelligent and stoic, yet kind at heart. He is oblivious to Tsumiki's crush on him, though he would at times makes romantic comments/gestures towards her. She is the closest girl to him regardless. He is responsible and independent. Like Tsumiki, he is a good cook, and is considered a genius. Io is naturally calm, but he apparently detests laziness or slacking in general, as he hit Mayoi on the head once when she came to his house to study, but instead turned to videogames.
He is usually seen spinning a pen with his hand at high speed, fast enough to catch Mayoi's surprise at his hand's speed. Pen-spinning seemed to be a hobby, since Io is very often seen doing it in the anime. At times, he (unknowingly) acts like a casanova, and thus is very popular with cats and girls. His popularity with cats may have been a nod to Tsumiki's more-than-obvious crush and reactions when close to him.
Io is emotionally dense, as he often fails to recognize Tsumiki's romantic attractions towards him and is unaware of the fact that his charm made him so popular with animals (specifically cats), claiming that his peaceful disposition made them happy instead.
He is also quite strong, though not shown as often as Tsumiki, as shown during Sakaki or Mayoi's pranks and antics.
In the manga, he is able to catch a fish with chopsticks, while in the anime, he is able to kill a mosquito with a toothpick. He also displays a lot more expressions and emotions than he did in the anime, as he seemed to panic when Tsumiki bit him on the head and was nervous when the girls (Hime non-inclusive) discovered his part-time job at Hatch Potch.
- Tsumiki Miniwa - Io is the target of Tsumiki's intense crush, though he almost always fails to see the signs, even when Mayoi teases both of them about it. Despite this, Io's attitude and disposition towards Tsumiki was a lot friendlier than towards other characters. Io thinks Tsumiki is cute, and would often give her a pat on the head in the anime.
- Mayoi Katase - Mayoi is one of Io's classmates, who likes to tease him and Tsumiki about the latter's crush on him. Unlike Tsumiki, who goes ballistics upon hearing the teases, Io remains calm and friendly towards Mayoi, despite disapproving of her antics. Io hit Mayoi once in the anime because she was lazing out, this is the first time Io was seen hitting someone else.
- Hime Haruno - Io's charming and stoic expressions often leads to Hime (and occasionally, Tsumiki) blacking out due to excessive nosebleeding. Hime is Io's co-worker at Hatch Potch cafe before Mayoi and Tsumiki discovered the shop. He apparently considers her a close friend, as he entrusted his part-time job secret to her (which she later failed to keep) and was also seen acting friendly towards her when she is hurt.
- Sakaki Inui - Sakaki is Io's best friend, and is almost always seen hanging out with each other. There seemed to be some sort of a rivalry between the two when it comes to videogames and sports, as Sakaki always strives to beat Io and are highly disappointed when he fails to do that. He occasionally goes to the arcade with Io after school and was aware of Io's part-time job (as Hatch Potch was owned by his sister Miiko).
- Advice To Girls Who Likes Someone(Ep. 4): "If you just act naturally with good intentions, surely he'll like you."
- To Ami(Ep. 4): "I Love You."
- To All Girls In The Classroom(Ep. 4): "I'm sure that tomorrow, You will all be even more beautiful than you are today."
- To Hime(Ep. 5): "Will you go out with me?" (Note: He wasn't actually asking her out, he's only asking her to join the Volleyball match)
- To Tsumiki, Mayoi & Hime(Ep. 7): "The instant when you smile is more beautiful, Than any fireworks could be."
- To Tsumiki & Hime(Ep. 10): "Be a good girl, and I'll make your heart skip a beat."
- From Episode 11: "I Shall Rid The World of Itching!"
- Io can spin an item fast enough to surprise Mayoi
|Tsumiki Miniwa - Io Otonashi - Mayoi Katase - Hime Haruno - Sakaki Inui|
|Saki Sakimori - Ami Kirino - Kikue Sakuragawa - Kyōya Saibara - Miiko Inui - Kana Miyama|