This is a documentary-style video of Mariru-chan, a modern girl with a stylish inner color, being transformed into a diaper-loving baby girl by her older sister, who acts as a lolita guide. While drinking strong diuretic tea and answering questions about urination, Mariru-chan can't hold it in any longer and wets herself while still wearing her clothes. After changing into girl's underwear, she wets herself again. It seems her older sister's suggestion that "adult bedwetting is exciting because of the shame" worked, as something other than urine appears in her panties. Mariru-chan's age is further reduced, and she's now made to wear a diaper. She wets herself again, and when her older sister discovers the wetness that's not urine, she gets a butt play. Even though her older sister has accepted that she's into this, Mariru-chan masturbates in front of her while still wearing the diaper. She rides her precious cock face-first and rubs her pussy furiously, resulting in a climax and bedwetting. Mariru-chan, now completely obedient, is made to wear a cloth diaper next. Although she's never seen a cloth diaper before, she finds it comfortable and enjoys the feeling of it against her butt. The baby powder also smells nice. She wets herself in the cloth diaper while cuddling with her older sister, who has become like a mother to her. She's now a complete adult baby!