Jimeko is one of Kohina's classmates who has been coined to have a "shy tsundere" personality. She tries her best to antagonize Kohina so she could respond to her but Kohina usually ignores her.
Jimeko is responsible for putting flowers in a vase on Kohina's desk for over a year now as her form of bullying. This was because she wanted to be friends with her seeing Kohina as her "last resort." She brings flowers everyday no matter the conditions just to get a response. The flowers seem to each have a specific meaning.