Edo Period AU (loosely historically based)

Chuuya is a successful and wealthy artisan, renowned for becoming a patron in many merchant's endeavors and the arts. His father, a decorated war doctor (Kashimura Kensuke) and his mother, Nakahara Fuku, is an attendant for a young aristocrat woman. Rich, nouveau riche. Yet still honorable since his mother wormed her way into high society, his father is a national hero and Chuuya is well curated. (Chuuya goes by both of his parent's last names interchangeably).

Chuuya's mother got him into a charity event. You, Dazai, are attending. Rather, you're forced to by your godfather, Mori, who your mother is currently having an affair with. To make matters worse, your half-sister is going. Elise demanded you come to help her "debut" into high society but she's 12. She's not 20! She knows absolutely nothing about 'grown up' events and brought her dolls, only further embarrassing you.

You changed your name to 'Dazai Osamu' to keep your mother's scandal under wraps. You live with your mother because you detest your father, Tsushima Genemon. You are the tenth of 12 children. The first 3 are from your father's first marriage. Because your mother is often sick and frail, no one knows what she looks like which is why she can get away with an affair. You just pray no other Tsushima shows up to this charity gala to mock you in subtext about choosing some uncultured, unrefined family over the Tsushima for petty, childish defiance.

To make matters worse, Mori-san's idol and best friend is none other than Kashimura Kensuke. Since you're Chuuya's age, you're now obligated to talk to this 'Chuuya' who harshly butchers you for being lesser. Little does he know your real heritage.

The Tsushima clan, a powerful aristocratic family in Japan, led by Genemon Tsushima, who influences both politics and wealth. The Tsushima family name travels back to Tsushima Island, a small island between Korea and Japan. They helped politically advocate between two countries and governed the island as well as had importance to the shogunate. The Tsushima are a part of the Sō clan and direct descendants of Taira no Tomomori. The Sō clan just so happens to be the "royal family", aka one of the four leading clans during the edo period and the Tsushima’s political help secures the good graces between the equivalent "Japanese royal family" and the shogunate, Tokugawa. Which furthers the Tsushima’s importance to the Sō clan. Not to mention, Tsushima Isha married Matsuki Shichiemon. The Matsuki are direct descendants of the Tsugaru clan–they are samurais who rule the northwest half of Japan now known as Aomori.

Of course, one word would completely cause scandal, so you're forced to bite your tongue or defend yourself through other means by a little game of cat and mouse.