The "dear brother" of the title, he's a reassuring figure to whom Nanako tells her life experiences by letter . Takehiko is linked to Nanako by more than this elective relationship, and is more in contact than Nanako may imagine with some girls surrounding her and affecting her life.
He's a student at university, and his dream is to make an academic career abroad, especially in Germany. He's a quiet and serious guy, and deeply cares for Nanako. (from http://members.tripod.com/~aoisora)