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[monochroid (モノクロイド)] 嫉妬(寝取られ堕ちた僕と彼女)

https://www.dlsite.com/maniax/work/=/product_id/RJ01223773.html

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This is the story of a Super Sentai hero who is seduced by an evil monster.

[Synopsis]

During a battle with multiple monsters, the hero of justice, Blue, corners a female enemy monster, Slime Reaper.
In a deserted building... the monster proposes to him.
"I want to have sex before I die".
Blue freezes for a moment at the unexpected words.
Sex between an evil monster and a hero of justice is an impossible act.
Naturally, he refuses.
However, the monster didn't propose without any hope of success.
It had been reported that Blue often gazes on female monsters' private parts.
The reaction is excellent...
The monster concludes this when he sees Blue's gaze fixed on her, even as he refuses.
Before he can think too much about it, the monster approaches him and sexually stimulates him.
The pheromones emitted by the monster and the pleasure caused by the stimulation slowed his thoughts.
''Just once... ''
Blue was so moved that he thought so...

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