It looks like you've shared the title of a blog post referencing something that translates roughly to "The Summer a Boy Became an Adult" (or similar), with "Vol.1" and a date code (-240906- possibly meaning September 6, 2024).
Transition to Adulthood: The narrative delves into the challenges and realizations that come with growing up. The protagonist's journey is emblematic of the struggles many face during this phase, including self-discovery, forming meaningful relationships, and dealing with the consequences of one's actions.
Anime (OVA): The animated adaptation began releasing in September 2024. The first episode, approximately 20 minutes long, was officially released on September 6, 2024.
Unique Twist: The story is often compared to a modern, eroticized version of The Strange Case of Dr. Jekyll and Mr. Hyde, with characters using "masks" to live out their truest urges without social consequences. Quick Guide for New Readers Original Creator: Jairou.
For readers interested in psychological drama and stories involving hidden lives, Volume 1 establishes a tense atmosphere centered on whether the truth will be revealed and how it will change the bond between the siblings.