Genma Senki Lexion

There used to be a fight between the king and the devil. That fight that split the sky and broke the ground, lasted 300 years. And there was a hero who tried to reconciliate the two rulers. He got both arms torn off, but the rules were so ashamed of themselves that they made peace and sent him their daughters as wives. Present time. Main character Akira inherited the power of that hero. On his 19th birthday that power awakened and he found himself in a bed with an angel girl and a devil girl. He's the only one who can withstand an invasion of monsters.