An undercover documentary exposes the staff of a bukkake-themed shop in Nishi-Shinjuku who instruct young girls on stain application to increase the value of their used underwear. Four teenage girls come to sell their panties and undergo the staining process to enhance their appeal. A lively, energetic Kansai-speaking beauty becomes aroused by the male instructor guiding her, drooling as she greedily sucks his cock after receiving her allowance. A healthy-looking girl in a school uniform writhes in ecstasy as her shaved pussy is touched to create stains on her underwear, eventually giving in to pleasure and surrendering her body after financial negotiation. Another innocent-looking girl in a sailor uniform reaches climax while using a toy to stain her panties. As the man penetrates her, she repeatedly cries out how good it feels, trembling her body in ecstasy like in a yoga pose.