Densou Genshi Mirukyua

Natsuki's older sister is really into an online game called "Real Breaker" but she can't play it for a while because she has to go on a business trip. The problem is, a super rare item called the "Mirage Stone" that can grant any wish is going to be released while she's gone, so she makes Natsuki play it for her (with a female character) and proceeds to make out with him before she leaves. After she leaves, Natsuki tries playing the game but is suddenly sucked into the the monitor and becomes the female character in the game. He's immediately caught by a tentacle monster and "raped" repeatedly (he enjoys discovering the pleasures of a female body) until he's saved by a beautiful female warrior. Where will their adventures lead them?!

(Source: BakaBT)