i love my older sister! natsu, my relative older sister whom i've always admired since i was a child. what was waiting for me, who returned home for summer vacation, was a person who was truly kind, as beautiful as dazzling, and was my first love itself. eating watermelon, cooling off on the veranda, sparklers in yukata... my heart doesn't stop pounding at her casual gestures and translucent sweaty skin. one day, i was seen with an erection in the bath... "it's my fault this happened, right?" natsu-chan smiled and took my hand...! after that, in the bedroom, in the japanese-style room, on the veranda... i cummed repeatedly in a sweat-soaked close contact, hiding it from my parents! before i knew it, my heart and body couldn't be separated from her... at the end of summer, the words we swore under the sparklers―― "this summer will be our secret forever." an unforgettable, one-summer memory that only we know.