Toudo no Ou to Sennen no Yume

There is a reason to exceed the time of a thousand years. Yasuhiro has a recurring dream since childhood. A dream of being poisoned by a middle-aged warrior. In a dream there is a terrible king wearing a heavy helmet made of animal bones. As he travels relying on the language in his dreams, he ends up reincarnating in another world... A ruthless beautiful king x a reincarnated Viking, a romance set in Kyiv 1,000 years ago.