Sakaki is Io's closest male friend and the other male main cast member. Together with Mayoi, he makes up the prankster duo in the friendship circle. He also has quite a competitive side; his constant goal being to beat Io, though most of his attempts are thwarted by either Io himself or outside forces. Sakaki also claims to love being outside and considers himself an outdoorsman.
One of the running gags throughout the series is that almost every object that leaves a characters' hand will end up hitting Sakaki, no matter how unlikely it may seem. He periodically makes sexual comments towards the female cast, although the comments are not well received, and sometimes just outright ignored.
His sister, Miiko Inui, owns a patisserie and cafe, where he works alongside Io and Hime.
Sakaki has short, orange-blonde hair and brown eyes. His height and weight appears to be average when compared to the rest of the cast.
Like most characters, Sakaki is usually seen in his school uniform. His other, more casual outfits usually consist of shorts and a t-shirt.
- Tsumiki Miniwa - His friend. Sakaki often hangs out with Tsumiki, though the two did not really share any interactions with each other, as Sakaki is more commonly seen around Io or Mayoi. Sakaki knows about Tsumiki's crush and sometimes attempts to help by persuading the emotionally-dense Io to go out with her.
- Mayoi Katase - His friend and pranking partner. They are also shown to be competitive when facing against each other. Sakaki is almost always the fellow conspirator in Mayoi's schemes, though their plans would occasionally backfire and hurt him. They both quite enjoy teasing Tsumiki and Io as a couple. Some of Mayoi's pranks regarding Sakaki would cause him humiliation and/or pain when they don't turn out well, though this is likely unintentional, as he holds no ill will towards her.
- Hime Haruno - His friend. Not much interaction was shown between Sakaki and Hime, though Sakaki is often on Mayoi's side when it comes to pranking Tsumiki and Hime. She does not seem to dislike him in any way though, and gives him friendship chocolate on Valentine's Day.
- Miiko Inui - Sakaki is Miiko's younger brother and one of the few that knew of Hime and Io's job at Hatch Potch. Miiko dotes on her brother greatly, which sometimes annoys him. Despite this, Sakaki still respects his sister and she also cares about him. Miiko has employed him as a server.
- Otonashi Io - 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 video games 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).
- Kyōya Saibara - His friend
- Kana Miyama -Sakaki is Kana's classmate and friend. Sakaki along with Mayoi are often seen coercing Kana into joining them in their antics, though she does not play along with them to the end and is not beaten up by the prank's victim (Tsumiki).
- Saki Sakimori - His friend.
- Kikue Sakuragawa - His teacher
- Ami Kirino - He was once featured on her show, alongside Io.
Also look in the Sakaki image section.