Naze ka?! Sweet Home

The protagonist, Kazuya, is sent to live with his married older brother Tatsuya to better focus on his exams. Not wanting to impose on the lovey-dovey couple, Kazuya refuses at first, but Tatsuya is very keen on the idea, so Kazuya eventually agrees.

However, Tatsuya is busy at work and often comes home late, if at all, leaving the younger Kazuya alone with his sister-in-law Minami most of the time.

Seeing Minami around the house constantly in various compromising situations, Kazuya has trouble concentrating on his studies. As you can imagine, he succumbs to the temptation… but this, too, is all part of his brother's grand plan! Tatsuya, who loves to dote on his little brother, just wants Kazuya to gain some solid experience(?) with a woman before heading out into the real world.

Just as Kazuya's "big bro-approved"(?!) relationship with Minami begins to bloom, Miyuki—Minami's mom—turns up at the house. Faced with the even more defenseless and debauched Miyuki, Kazuya cannot begin to hide his confusion at which of them he prefers. It doesn't take long for the easily swayed Kazuya to start sleeping with Miyuki, too.

To complicate things further, Aunt Kasumi, only daughter of the Fujiwaras, is next to arrive at the harem home of the Yoshiwara brothers. Tatsuya harbors deep distrust towards the Fujiwaras ever since they attempted to take guardianship of Kazuya, and is soon fighting with her like cats and dogs.

So what is Kasumi scheming exactly...? And what does the future have in store for our protagonist, thrown into this exhausting predicament at a crucial time in his life?! Harem problems can be tough...