However, I suspect that you might be referring to a specific anime, manga, or light novel series titled "Ane Oyako de Iku" (also known as "Going with an Older Sister" or "Elder Sister Trip").
The anime series, produced by Studio Fantasia, consists of 2 OVA episodes released in 2005. The story follows Masamune, a high school student who becomes involved with his older sister's friend, Natsumi, who is a few years older than him. As they spend more time together, their relationship deepens, and they embark on various misadventures. -ENG- Ane Oyako de Iku-
The series has received mixed reviews from fans and critics. Some praise the series for its lighthearted and entertaining storyline, while others criticize it for its ecchi content and perceived underdevelopment of characters. However, I suspect that you might be referring
A very specific and interesting topic!