Chained Soldier

In a world where heroes are born, not made, Ein’s god-given gift is the weakest: the power to appraise things. Treated cruelly by his peers, Ein spends his days in self-abasement—until he meets Yuri, the spirit of the World Tree. Yuri and her protector, Ursula, bless Ein with the Spirit Eye, unlocking new strength. As his abilities grow, Ein embarks on a journey to uncover his true purpose.

For 30 years, thousands have traveled to other worlds. The few that return keep the powers they had in those worlds. Akatsuki Ousawa returns from the world of Alayzard with the defeated Demon King's daughter, Miu. Miu pretends to be Akatsuki's sister to hide her true identity. They join Babel, a school for inter-dimensional travelers, and struggle against the student council to uncover the truth behind the school.

One day, humanity was invaded by another world. Having experienced that battle, known as Other World War I, humanity moved to marine floats, built for emergency evacuation purposes, as soon as Other World War II began. It's around that time that Kizuna Hida is summoned by his elder sister and visits the Strategic Defense Academy Ataraxia where he meets Aine Chidorigafuchi, a girl who uses Heart Hybrid Gear Zeros to fight the otherworldly enemies. He has a tough time dealing with her, but when her Gear runs out of energy, the only way to get it back in action is to do something lewd to her!

Witches were once respected for the wisdom and magic they gifted to humans. But with the rise of the Gear Expansion era, the new science community deemed them as enemies who hindered the progress of society. Thus began the slaughter of all witches, including one who had mentored a human boy named Adonis. After witnessing her death, Adonis vows to bring bloodshed and terror to the human race.