Gang no Kaikata

One night, just when he was leaving work, Sugimori Yuu ends up meeting a very aggressive-looking foreigner by the name of Clyde. When he sees himself being threatened by a gun, Yuu has no option but to follow Clyde's instructions, so he takes him to his own house. And, after a little talk, they came to the conclusion that Clyde "travelled in time." From then on, Yuu really doesn't care if it's true or if it's a lie; he offered him money and food in exchange to at least spare his life. But Clyde...

(Source: Ichijinsha, translated)