Cheerful Amnesia

Cheerful Amnesia is a manga series that started in 2016 and ended in 2020.

Chapter 0
Mari is shown completely naked while asking Arisa if she'll take a bath, causing Arisa to get embarrassed. Arisa then notices that her breasts have grown while undressing to take a bath.

Chapter 1
Arisa struggles to figure out which bras are hers and imagines Mari in some of them. After Mari returns home, she reveals that all of them are Arisa's leading her to believe that Mari doesn't wear any while imagining her undressing without any underwear. Mari then undresses in front of her to show that she is wearing underwear which Arisa bought for her.

Chapter 3
Arisa imagines herself telling Mari to kiss her while they're both wearing BDSM outfits.

Chapter 4
Arisa takes off Mari's shirt after she accidentally spills a can of sprite on it, revealing her bra. Mari later wakes up topless

Chapter 6
Mari removes Arisa's shirt in order to wipe the sweat off of her torso. Arisa gets embarrassed when her front is cleaned. Later, because Mari sprained her fingers, Arisa had to take off her clothes for her, including her underwear. Afterwards she helped her to bathe but got embarrassed when she had to clean her front. Mari gets aroused when her vagina is washed.