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My girlfriend's older sister invited me ~Even though I told her to go all the way~ Separate edition

The main character injured his arm in a club activity and was shut in even though it was summer vacation.
His girlfriend, 《Arisa》, is on a trip and sighs that she can't even pull it out by herself.
Then, Chisa's sister, Nanami, comes to visit.

She told me that she was asked to take over for Arisa while she was on vacation.
She immediately wipes his body, but his crotch reacts to the way she does it and .......

SHe said, "Ah... well, you're a boy. If it's been a while, I'm sure you've stocked up."

"I'll take care of it for you. Since I've agreed to take care of you, I have to take responsibility for things like this, right?"

At first, it was supposed to be just "taking care of you," but after that day, the two of them start to get into a physical relationship.
This complicated relationship continues in secret even after his girlfriend Arisa returns home. ......

Chinese version (Complete): https://e-hentai.org/g/2569232/33b8fc1dd5/