Episode list

Kyle finds himself transported four years into the past to the beginning of the demon invasion, right as he was about to finish off the final boss. Armed with the memories and skills he gained in that time, he'll endeavor to prevent the same tragedies from occurring.

A killed detective's mind is transferred by a scientific genius into the body of a shape-shifting robot superhero who fights crime.

Hayate is still working as the Sanzenin Butler and this season features a lot more Hinagiku, as scenarios that include herself and Hayate allude to potentially mutual feelings between them. Nagi is also interested in escalating her relationship with Hayate, since Nagi's perception of her relationship with Hayate remains based on the miscommunication that occurred on their first meeting.

To combat the terrorist organization known as "USR", eleven countries combine their naval forces to form the Peace-Keeping Navy (PKN). However, all hell breaks loose when Admiral Red and his USR submarine UX crash the PKN's inaugural ceremony and destroy majority of the fleet. At the last minute, when the UX lands the final blow on the aircraft carrier Apollo-Norm, the obsolete Japanese submarine 707 (a.k.a. "Snapping Turtle") appears from out of nowhere and sacrifices itself to save the PKN flagship. Six months later, Captain Youhei Hayami is called back to duty to lead a new group of recruits and captain an all-new 707 in the war against terrorism underwater.

In a world divided between angels and evil creatures, only the young hero Yamato Shintei has the power to defeat demons ...