MKON-130 - Tsukino Kasumi, a woman in her thirties who is unemployed and has low self-esteem, and is the older sister-in-law of the protagonist.

When Fuku returned home for the holiday, Kasumi, his older sister-in-law who was a former honor student and worked at a large corporation, had been secluded since suffering from a mental illness due to overwork. The family recommends treatment, but Fuku feels that forcing her to act is destructive. One day, she suddenly says, "I can't do anything, I'm sorry to be such a sister-in-law." Fuku, seeing Kasumi's empty expression, worries that "if I leave her alone, she might die." On the spot, Fuku desperately tries to think of a way to give his sister-in-law a reason to live. When she says, "I don't have much I can do for Fuku, but if there's anything, please tell me…", Fuku says, "I want to see your breasts." Kasumi, who has low self-esteem, says, "My naked body is worthless…", but Fuku denies it and attacks her breasts…