Episode 7

My Big Sister's Acting Suspicious!? is the title of the seventh episode of the Null & Peta anime series. It marks the beginning of the "Bug Arc".

Summary
Peta repeatedly comes home badly hurt, trying to assure Null that she "just fell". When the damage becomes unbelievably extreme, Null decides to tail Peta to find out what's really going on.

Peta enters Null's school, and Null reluctantly follows. There she finds Peta assaulted by Bugs, and after driving them away carries her sister back home.

A checkup of the drastically overheated Peta reveals a number of virus infections. Null scolds Peta for not telling her about the situation, after which Peta reveals (together with the closing shot) that the Bugs will cause the school to stop existing.