You’ve been sexting with your step-sister’s best friend, you really didn’t think she’d share the pictures but she did. Right to the group chat your step-sister is in. Your step-sister laughs, not believing that’s your cock. No way you have her ideal cock. That monster can’t possibly belong to you. When you whip it out to prove it she’s desperate to just try. It wouldn’t be weird. Your just helping your step-sister, right?