In the manga, the only one that's gotten yandere with Shizuka over Tomoko is, surprisingly, Emily Uchi. She even said "don't get cocky, bitch!" when it was obvious Shizuka was charming Tomoko. The humour there is that this is exactly what Shizuka went through with other girls in middle school and the BOYS they were interested in, who were swarming around Shizuka. Now, she has to deal with the Lesbian Edition®