Mayo-chan

Mayo-chan is the mascot of 0verflow.

Appearance
Mayo-chan appears as a chibi-fied catgirl with magenta hair, cat ears, and tail, and pupil-less blue eyes. She almost always wears a blue jumper.

Snow Radish Vacation

 * On Hatsuka's hoodie

Summer Radish Vacation

 * In Youko's travel bag

PureMail OVA

 * On Kei's mousepad

PureMail After

 * Sitting at the oden stand while Kei confides in Shinichi.

Imouto de Ikou! OVA

 * In the first episode, Mayo-chan can be seen peeking within the mess Akiho makes of Hisashi's kitchen. Mayuka also wears Mayo-chan slippers as she cleans up said mess.
 * In the second episode:
 * Fuyuno prepares rice with a Mayo-chan rice grinder.
 * Haruru's doctor is seen wearing a Mayo-chan pin on his tie
 * Sleeping as a plushie in Mayuka's bed.
 * On the minute hand of Hisashi's alarm clock.

School Days anime

 * In several episodes, Mayo-chan mascots appear handing out fliers, and Sakakino High is seen to possess many Mayo-chan costumes
 * In Magical Heart Kokoro-chan, Magical Heart and Magical Word summon and pilot a mecha Mayo-chan to battle against a giant Tanaka

School Days manga

 * In Chapter 6, Sekai shoots a Mayo-chan figurine with a cork gun as part of a festival game

Shiny Days

 * On a movie poster within Radish