The chapter you are looking for is of the manga "Boku ni Harem Sefure ga Dekita Riyuu" (The Reason I Could Get a Harem of Friends with Benefits).
[Ail] Boku ni Harem SeFri ga Dekita Riyuu 5 - E-Hentai Galleries
The series features a variety of characters that represent different social roles: boku ni harem sefure ga dekita riyuu 5
Since the series is an adult manga (H-manga), it is typically found on dedicated adult manga sites or via the original anthology releases (usually Comic Bavel or similar publishers).
Different volumes have been released periodically, often accompanied by supplemental materials for fans of the series. The chapter you are looking for is of
If you're looking for:
Various younger characters who represent the protagonist's school life and contribute to the energetic tone of the series. If you're looking for: Various younger characters who
Here is a summary of what typically happens in this chapter (based on the standard numbering of the fan-named "Harem Time" arc):