The samurai, An Legendary Adventure Tale Part 1

the story begins with Takashi "Shiro" Shirogane, a 21-year-old young man who falls into a well in an abandoned shrine after his boyfriend, Adam was missing, falling an argument. He is magically transported to a land named Altara, a dimension surrounded by magical creatures called daemons, where he meets the half daemon named Keith who helps him try to adapt to this world and protect the quintessence Crystal that was embedded in his right arm while discovering the first true love of his life and finding things that are important to him as well as trying to defend the planet, while Keith on the other hand, is dealing with a betrayal that seals him to a tree for the years to come and the loss of his lover. Because of that, he's planning to become a full deamon to defeat the Galra Empire.