18-Sai, niizuma, furin shimasu

Asuka is the heiress to a massive estate, called the Sanjou Empire. With her high school graduation, she is to marry her bodyguard Akira, and she is starting to think her actual budding romantic feelings are pointing elsewhere, but can that really be true!?

source: https://www.mangaupdates.com/series/07si1oo/18-sai-niizuma-furin-shimasu