Everybody goes to the ocean for a summer festival and the guys sneak off to a cursed island.

In the series, Light and Yomi are spending their daily lives happily playing video games. One night when everyone else is asleep, Light receives an invitation from Alpha, a messenger for someone named King. Light and Yomi are then sucked into another world, where they must undertake a quest to rescue Princess Melody from the demon lord. Light thinks this must be his destiny, while Yomi thinks it's kind of annoying. They form a party with Alpha to start their quest. Alpha as it turns out is an AI robot, and he has a program that allows them to raise their levels while slowly continuing their adventure. (Source: ANN)

Monsters known as "Horrors" have invaded the world, entering through gates from the Makai Realm of Darkness. These corrupt, demonic creatures have the ability to seize human bodies and feed on their souls. Citizens who are out past sunset will likely never see the sun rise again, but those who live in the capital city have no need to worry—they are protected by a spiritual force field created by the sorcerer group Onmyouji. In possession of legendary armor, the Golden Knight Raikou proclaims that he will protect everyone from the Horrors. Accompanied by his attendant Kintoki and the mysterious Makai Alchemist Seimei, he strives to become a formidable Makai Knight, but Raikou is ill-prepared to handle the side effects of the armor. Disappointed by his own shortcomings, he sets out on a journey of self-discovery to master his weaknesses and prove his worth. [Written by MAL Rewrite]

In the 21st century, the characters of Fist of the North Star are living in peaceful Japan. In particular, Kenshirou is a convenience store worker, Raoh works at a factory, and wracked by illness, Toki is looking for work. The legend of the Fighting NEET (Not in Education, Employment, or Training) North Star begins in the modern day. (Source: Crunchyroll) Note: Short stories adapting Hokuto no Ken: Ichigo Aji manga are included at the end of each episode. Serving as a spinoff gag manga of the original Hokuto no Ken series, the story is a parody of Fist of the North Star by Buronson and Tetsuo Hara. It consists of page-long gags centered mainly on Souther, both within his final battle with Kenshiro and inserting himself into other parts of the series where he doesn't belong. One recurring gag involves the kid with a turban repeatedly stabbing Souther in the leg every time he climbs the pyramid's staircase, and another involves Rei suddenly transforming into Souther in his iconic moments. (Source: Hokuto no Ken Wikia)