Mou Hitotsu no Umi
もうひとつの海
Five chapters in total, with the first two being on Karino Yoshihito*. Third chapter's kinda on him too, but it's from the point of view of a classmate. Chapter 4's an innocent story of a girl who has to learn how to swim (school life tag's for this chapter and the previous one). The ending chapter is a short slice of life piece on the mangaka's experience with colors and painting since young.
*recurring main character in some of Nishi Keiko's stories; see "Mizu ga Kooru ni Naru Toki" and "September"
(Source: MU)