Nante Suteki ni Japanesque: Hitozumahen

Ruri, the hopeless daughter of the great General Fujiwara, vows to "be single forever" after the death of her first love. However, the General plans to force Ruri into marriage, whether she likes it or not. Not wanting a forced marriage, Ruri decides to find a nice boy to marry instead. Ruri's chosen candidate is Taka-akira, a boy from a prominent family and a close friend to Ruri's younger brother. With her problems apparently solved, Ruri and Taka-akira decide to get married. Unfortunately, things aren't as simple ans they seem and life has even more complications in store for the young couple...

source: https://www.mangaupdates.com/series/w3vyjm3/nante-suteki-ni-japanesque-hitozumahen