English Summary:
"Suck it nicely, you weakling!"
The one servicing that bastard's thing was my beloved girlfriend. There was nothing I could do before that scene...

After starting to play an erotic game recommended by a friend, Mitsuki falls head over heels in love with the game's main heroine, Kotoha.
But this game is a NTR game in which the heroine is seduced by the player's best friend, Ryo?!

While searching for a happy ending with Kotoha, Mitsuki accidentally falls onto the train platform.
When he wakes up, he finds himself faced with none other than... Kotoha!?
To his surprise, Mitsuki has been reincarnated as the player character of "that" game...!

With his vast knowledge and love of games, Mitsuki is determined to change fate this time.
In order to protect Kotoha and the others from Ryo, he must achieve a perfect happy ending!

Japanese Summary:
「上手にしゃぶれよザコ×××！」
クソ野郎のアレに奉仕するのは俺の大好きな彼女。その光景を前に俺は何もできず…。

友人の薦めでとあるエロゲーを始めた光希は、作品のメインキャラ・古都葉にガチ恋をする。
だがこのゲーム、ヒロインがプレイヤーの親友キャラ・凌に堕とされる寝取られゲーで！？

古都葉との幸せな結末を探し求める中、誤って駅のホームに転落してしまう光希。
目覚めた彼の眼前にいたのは、他でもない…古都葉！？
なんと光希は「あの」ゲームのプレイヤーキャラに転生したのだった…！

膨大なゲーム知識と愛で、今度こそ運命を変えようと決意する光希。
凌から古都葉たちを守り抜き、完全無欠のハッピーエンドを迎えるために――！