The cover of the collected volume
Togainu no Chi ZERO is one of two official manga adapted from Togainu no Chi, the other being titled simply Togainu no Chi. (There is also a manga adaptation of Togainu no Chi True Blood, using the same name as the game.) This manga follows Keisuke's route. It was written and illustrated by Kana Yamamoto and first published in 2005 in Magazine ZERO.
After its completion at four chapters, it was collected into a single volume. It has not been officially licensed in English, but it has been partially fan translated.