He rewards them for their friendship.

Deciding that since his new powers will allow him to keep them in line, Issei makes a few statements:

"It is normal for Matsuda and Motohama to be able to look at porn and peek on changing girls whenever they want. It is normal for them to not touch a girl unless I approve or the girl has feelings for them."

There. That should prevent them from going crazy with their new perverted freedom.

Of course, he had his own needs to think about too... "It is normal for women to be perfectly willing to have sex with me if I want them to."

Seeing his friends immediately stop studying and begin watching him grope the Kendo club girls breasts with perverted leers, Issei debated what to do next.