Ultra Maniac OVA.

Ayu Tateishi is a popular second-year student at her middle school admired for being calm, cool, and collected. But this carefully preserved image was all crafted to catch the eye of her crush Tetsushi Kaji, who once complimented her for those qualities. Studying, playing tennis, and finding chances to speak with Tetsushi are all that are on Ayu's mind—until the day she finds a mini-computer underneath a bench.