Warui Otona Mihon 

There was only one person who vexed the whimsical happy-go-lucky middle-aged shop owner of a traditional sandal shop, Takigawa Tetsuya, to the end: Kudo Rui, a part-timer of his shop! Tetsuya came to his bishie part-timer's rescue after his fight with delinquents. To repay for his kindness, Rui helped out in Tatsuya's shop. However, the carefree Tatsuya had to restrain himself from preying on the angelic Rui... until one day his control finally snapped– (Source: Houbunsha, translated) Note: Includes an extra chapter.