Aka x Kuro

A 17-year-old named Renji Shiba trains at a kickboxing gym, where he is highly regarded by his coaches and confident in his skills. However, with no one able to challenge him, he loses interest in fighting. One evening, after leaving the gym, he is attacked by a man wearing a Noh mask and left unconscious. After regaining consciousness, Renji becomes determined to find and fight this new opponent again. The manga includes three additional chapters titled "Max," "Box," and "Kix."