Crazed Fruit aka Kurutta kajitsu

Natsuhisa Takashima and Haruji Takashima are young adult brothers living in Tokyo. Natsuhisa and his friends are bored and restless and don't see much hope for their future, while younger Haruji at least sees the possibility of a bright future for himself. Both brothers are interested in the opposite sex with Natsuhisa's interest being more animalistic and constant while Haruji's is more innocent. While they are out together boating one day around Sagami Bay, they spot a young woman with whom Haruji is immediately attracted but who Natsuhisa pays little attention. She is twenty year old Eri. Natsuhisa encourages his brother to pursue her, which he does slowly. In the time they end up spending together, Haruji and Eri, without telling each other so, start to fall in love with each other. A specific incident makes Natsuhisa look at Eri in a different light, he who secretly begins to desire her himself. Something that Natsuhisa and his friends discover about Eri leads to Natsuhisa using the information for his and what he tells himself being Haruji's mutual benefit, albeit in different ways. What happens if discovered has the potential to destroy Haruji emotionally, in he way he views Eri, women in general and his brother.