Oni-san Kochira!

Suddenly, the demon Tamon and his servant Yakusha appear before Kito Akito, a lonely and unlucky middle school student. Tamon's heart was once eaten by Akito's ancestor, and now he has only one year left to live. He says he has come to take Akito's heart as his descendant. However, Akito's heart is extremely weak due to repeated misfortune. Tamon realizes that his heart becomes stronger when he feels happy, so he reluctantly moves in with Akito to strengthen his heart again... (Source: Shinshokan, translated)