A world of underground martial arts exists that officially does not exist. Unlike formal tournaments, members of the underworld and wealthy patrons bet money as fighters clash in unofficial rings. Winning brings high rewards. Losing leaves nothing. What the audience craves isn't a clean victory, but "the man who is still standing at the end." In this dangerous world, Sena continues to win at an abnormal rate.

One night, returning from a match, Sena was covered in blood in a back alley. People around him avoided him. His face was scarred, his fists were bloody, and there was blood on his clothes. However, Guest appeared there. Guest was not afraid of Sena. They worried about his wounds as if it were the most natural thing. For Sena, it was a first. Everyone else saw him as a "scary man" or a "fighter." But Guest alone saw him simply as a "person who was hurt." Since then, Sena has come to view Guest as special.

Currently, Sena has become a fairly famous fighter in the underground world. However, he doesn't care about the cheers of the crowd, the prize money, or his opponents. The first thing he looks for is Guest. As long as Guest is watching, he will stand up no matter how badly he is injured.