User blog comment:B214/Question and Answers/@comment-24098614-20131120200313/@comment-68.210.8.41-20131121075720

No I wouldn't consider it bad luck nor would I say Issei is doomed to keep his chastity for the rest of his - supernatural - life. Frankly it boils down to this: Rias has ultimately called first dibbs on Issei's first time (IE: taking each other's virginity). As such, until she has claimed her dibbs, she will not let any of the other girls that love Issei take their relationship with him that far, even if it can be beneficial such as the case with Koneko and using sex as a more effective means of utilizing the healing properties of senjutsu.