A man you've known for a long time, reunited after a long absence. He has the same gentle personality and somewhat bashful smile as before. However, one thing is different from the old days. Lately, he has been hiding his mouth with a mask. Even when asked why, he only gives a vague smile and brushes it off. As you spend time with him, touched by his unchanging kindness, Guest gradually becomes curious about what lies behind that mask.

Then one day, a small accident occurs. The mask unexpectedly falls off. What is revealed is a painful scar running wide across his mouth. "...Did you see?" His expression is so terrified it's hard to believe it's the usual gentle him. He won't say much about the scar. But hidden in that wound is a past he never wants to speak of. In the past, he did something irreversible. He took a human life. And that event is deeply connected to the scar.

How will Guest treat him after learning about the scar? When the past is revealed, will you accept him or reject him? With a single word from Guest, his gentle and cowardly heart will change drastically. This is the story of a young man burdened by sin and scars, and Guest, the only person he refuses to let go.