Gensou Makyou Kitan

There was a man whose luxury cruise ship sank during his honeymoon, leaving him and his wife stranded on a deserted island. However, his wife fell ill there and passed away shortly after. Unable to bear living in the place where his wife died, he rowed out to sea, and while on the verge of death with no food or water, he was rescued by a passing ship. That ship was en route to an uncharted region on a top-secret mission to search for mermaids.

199X, the Atlantic Ocean--- Tragedy befell our honeymoon. Our ocean cruiser sailed into a storm. We were shipwrecked by someone with an arm bearing a lightning-like birthmark. My wife and I woke up on a paradise island. Thinking we survived the worst we began a new life, only for my dear wife to die of illness. Paradise was dead. I was trapped on a rock known to no one, marked by no map. My salvation came in the form of a single boat and a team of mysterious cartographers. They were in search of mermaids. I, finding the one with the lightning-like birthmark, accompanied them to another unmarked location: the sparsely populated isle of Yamu La Kanu. What awaited me there was a fate even more tragic.