From game : Grandblue Fantasy

The story is set on one day during summer vacation. It follows a group of boys who try to view a fireworks display from the town lighthouse to see if they look round or flat when viewed from the side. Meanwhile, one of the boys, Norimichi, receives an invitation from his crush Nazuna to run away with her.

Suddenly a high school student Subaru Natsuki has been summoned to another world on the way back from the convenience store. With the biggest crisis of his life being summoned to another world and no sign of the one who summoned him things become worse when he is attacked. But when he is saved by a mysterious silver-haired girl with a fairy cat, Subaru co-operates with the girl to return the favor. When they finally manage to get a clue Subaru and the girl are attacked and killed by someone. Subaru then awakens in the place he was summoned and notices the ability he gained "Returns by Death" a helpless boy that only has the ability to rewind time by dying. And beyond the despair can he save the girl from the fate of death!

From MangaHelpers: In a strange twist on Arthurian legend, young Art pulls the magical sword Excalibur out of a stone--only to find himself as one of a million Arthurs, fighting to defend the island of Britain from enemies and to earn the rank of the true king. Art is pretty puny, but his childhood friend Ligu (who was also chosen by an Excalibur) tries to keep him from being immediately killed. Soon Art lives in a castle with knights, which are created beings who serve the kings. From the respect with which he treats the knights, he inspires some to hope he becomes the true king. But is that really achievable by a scrawny crybaby like him? [tethysdust]

The meeting between a normal boy and a witch liberates the world from its curse...I'm a magic apprentice. "My master," who has been living under this same run-down roof with me, is a shut-in girl who proclaimed herself to be a great witch. Despite sounding all high-and-mighty, my defenseless master loves to watch her disciple cooking for her. Our daily lives, filled with happiness, go by quietly. However, little did I know that behind that quiet, happy daily life is a terrible secret that involves the fate of the world...

Deep in the unexplored reaches of the dungeon, a corpse is discovered—one that shouldn’t exist. After Iarumas is resurrected, his memories of life before death are gone, and he spends his days delving into the dungeon to retrieve the bodies of dead adventurers. Can they be revived as well? Or will God reduce them to piles of ash on the altar? Either way, Iarumas collects his finder’s fee. And though his skills earn him some grudging respect, he’s also scorned for this cold, utilitarian attitude. The living keep their distance—Iarumas consorts primarily with the dead. That is, until he meets Garbage, a feral young swordswoman who’s the sole survivor of a massacred party. With Garbage by his side, Iarumas ventures deeper, scouring the dungeon for clues to his past, avoiding monsters, traps, and the inevitability of a permanent ashen demise.