For anyone who enjoyed this series, I really recommend basically any manga from the writer, Satoshi Mizukami. Specially his "big three": Hoshi no Samidare, Segoku Youko, Spirit Circle. This way of handling plot as a result of characters and their relationships, and characters as a result of everything that led to this point, is a trademark of his. His longest series are great because he really has the time to develop and explore these connections, but even his one shots manage to do so in a concise and satisfying manner.