Sakiko Takashima

Sakiko Takashima (高島 早希子, Takashima Sakiko) is the manager of Kaimei High School's baseball team who was blackmailed into smashing classroom windows during the "Glass Man" incident.

Backstory
When Sakiko was still in Miya Middle School, she was overweight and looked completely different from her current appearance. She fell for the same boy that Saori was interested in, and each wrote the boy a love letter. When Sakiko went to put her letter in the boy's shoe locker, she found another letter already there (Saori's) and unconsciously took it, crumbled it up, and threw it away. She left her own in its place, though she never received a reply from the boy.

The "Glass Man" Incident
When the baseball team comes under suspicion of having smashed a number of classroom windows, the Sket Dan question Sakiko about which members practice in the early morning. It later turns out that she has been the one smashing windows, as someone had used pictures of her from middle school to blackmail her into doing so. Not wanting her boyfriend Eiichi and the rest of the school to learn of her old appearance, she had complied. To push suspicion away from herself, she spread the "Glass Man" name - knowing that, since the members of the baseball team were all innocent, no evidence would be found to convict them.

When Bossun notices a discrepancy between the first character of the final window and the last character of Sakiko's name, he discovers that the pattern of room names spelling out the culprit's name has been broken. Realizing this occurred because the one blackmailing Sakiko was following the Sket Dan's reasoning on the case, he reveals the broadcasting club's camerawoman Saori as the real culprit. Having twice fallen in love with the same boy as Sakiko and twice been unable to grow close to them, Saori had grown to hate the other girl. In the end, however, they reconcile and the Sket Dan take responsibility for the incident to protect both girls.

Etymology

 * The name Sakiko means "already, now, early" (早) (sa), "hope" (希) (ki) and "child" (子) (ko).
 * Sakiko's surname Takashima means "tall, high" (高) (taka) and "island" (島) (shima).