Their relationship seems to be initially hostile as their first encounter in Volume 5 when Kuroka tries to kidnap Koneko and as a member of Khaos Brigade. Kuroka attacks Issei and overwhelmed him, taunting Issei that he's much weaker than Vali. When Issei attained his Balance Breaker, however, he became powerful enough to withstand her attacks, much to her surprise. While he stops his attack just before hitting her, planning to show her mercy, he declares that he will not stop next time if she tries to take Koneko.