If you're looking for manga similar to Da Capo III (Rino FUJII), you might like these titles.
Akira is a high school student. He belongs to an astronomy club and enjoys his school life with other members including Kotone. He loves her, but can't tell it to her. As summer comes closer, people around him fall in love with someone. What will happen to his love...?
Hoshiuta is set in the fictional town Mihoshi in Shizuoka Prefecture, Japan. The town is in a quiet, rural area on the west of the Izu Peninsula and borders the Suruga Bay. There is a high school named Mihoshi Academy in the town. The protagonist Kazuhiko Suoh and his friends are students of the school.
In the near future. In a not so distant place. There exists a society where law is based upon deterrence and criminals are assigned "obligations" fitting for their crimes. Within this society, a man named Morita Kenichi aspires to the position of Special High Class Individual, one who holds authority over said criminals. For the purpose of fulfilling his ambition, Kenichi returns to the town he once called home. There he will encounter three girls bearing "obligations" and the past he left behind. Won't you join him in this story about how people relate to their society?