Nazotoki-hime wa Meitantei♥
Japanese title: ナゾトキ姫は名探偵♥
Alternative titles: Nazotokihime ha Meitantei
Type: OVA
Source: Manga
Episodes: 6
Status: Finished Airing
Aired: Aug 3, 2012 to Dec 27, 2013
Duration: 12 min per ep
Rating: G - All Ages
Studios: SynergySP
Genres: Mystery
Demographics: Shoujo

The story centers around Hinami, a bookish, eyeglasses-wearing girl, and her two friends. When there is a mystery to solve, she transforms into the clever Nazotoki-hime (literally, Princess Mystery Time). 

(Source: ANN)