The top reason for a couple's breakup is sexual incompatibility...?" Jun, who just got a boyfriend, feels insecure about her own skills... Practicing together with me (her brother) who lives together!? "I don't want to be disliked by my boyfriend, so let me practice with my brother," and that one sentence begins the illicit relationship between siblings! The sister, who tries various fellatio techniques she found on the internet, but I was supposed to be immune to my sister's fellatio... There shouldn't be any... At first, it was just supposed to be 'practice', but before I knew it, I was just being licked and teased endlessly...!
