Ninin ga Shinobuden

ニニンがシノブ伝

Kaede is a normal school girl who was studying for her exams for school when suddenly she is interrupted by Shinobu, a girl who is a ninja-in-training, attempting to complete her exam. The problem is, in order for her to successfully complete her exam, she must steal one of Kaede's panties!

In Kaede's attempt to stop Shinobu from stealing her panties, an unexpected friendship is forged between the two. Kaede soon becomes engrossed in Shinobu's world, surrounded by partying ninjas and a yellow pac-man like thing by the name of Onsokumaru, who claims to be the master of all ninjas!

(Source: MAL Rewrite)