Story: You know what? Skip the story. You aren't here for the overall thing and the most I know is "This adorable girl, so cute and adorable- likes this guy but is too shy and tsundere to confess. With their friends, since they hang out and all, hijinks ensue". See? It's the usual premise for a show about comedic hijinks based around a group of adolescent friends but it works. It's funny, it's heart stoppingly cute and pretty damn entertaining. For here, more on writing than actual plots.
The events they partake in, all the usual stuff; festivals, physicals, camping trip with that cabin they all stay in, has all the staples but it does it well and the manner it does it in is pretty spiffy. Turning a game of volleyball or air hockey into something awesome or mundane sutuations into something no sane person would do all adds to it and makes it more of a joking slapstick school comedy than just mere comedic school life fare. That sense of wackiness, ya know?
And those Kindergarden bits at the end, HOLY SHIT IT'S ADORABLE.
Animation: Oh good lord. Tsumiki, Tsumiki, Tsumiki. I cannot say it enough, she is so, so, ridiculously adorable. As a petite gal, she's cute, almost overwhelmingly so. But add in some cat ears, a cat tail and she becomes-
It should be illegal to be that cute.
Everything else is fine and dandy but not overwhelmingly detailed. It's real nice to look at and pretty charming in it's own right. Little visual quirks, constant cat smile with Mayoi, Io's awesome pen spinning, visual gags and those running visual gags make up for the easy-on-the-eyes animation.
Sound: I love my gratuitous English and this has it in good amounts. That snowball episode and Mayoi come to mind and the VO overall do a pretty dang good job. Verbal tics included, especially nya. The OP I adored and was... childish? Zany? Suited it at least, and it really worked for me but EP's not as memorable.
Characters: Tsumiki is the personification of moe. It's moe to the umpteenth degree that makes me squee and oh my god, it's so ridiculously adorable! So adorable. This show's not high on development but the characters are so lovable that it hardly matters. From the chaotic duo Sakaki and Mayoi to the stoic awesome of Io, the nose bleeding naive Hime and the rest, they sell the show and make it fun.
Overall: Ridiculously cute, fun, funny and an enjoyable school comedy with hints of romance and the lovable tsundere where everybody knows her crush but the object of her affections.