واکابا تسیوکیشیما

Second daughter of the Tsukishima family, in 5th grade in Part One. Through their childhood, Wakaba is constantly with Kō. She constantly talks about their future together, even giving him a schedule of suggested future birthday gifts that includes an engagement ring for her 20th birthday. She frequently kisses Kō, which annoys their mutual friend Akaishi, who has a secret crush on her. For several birthdays in a row, Wakaba gives Kō alarm clocks because he has a hard time waking up in the morning.

[Spoiler: She dies in a swimming accident while at a summer camp during 5th grade.]

Her name means "young leaf".