Ecchi no Renshu wa Uwaki ja Nai yo ne?

It's not cheating if it's sex practice! Just make sure you don't enjoy it too much, and use techniques like "finger-sucking" and "just the tip" to avoid getting too close to the real thing. But if you slip up and accidentally let your friend's boyfriend pour his cum in you, that's okay. It's only practice. (Source: Irodori Comics)