Kemono na Wakagashira wa Dokusen Yoku wo Kakusanai

Tsubaki, a high school girl whose grandfather was the head of a yakuza clan, had a crush on Kujo, a top man in the gang. She wanted him to see her as a woman, but he always treated her like a child. Then, Tsubaki was given the big responsibility of nominating the next head of the clan. Kujo protected her during the battle for leader, but when a marriage proposal with a rival clan was made, his attitude changes drastically! He was the man who had protected Tsubaki for all this time, too long to let anyone else do this to her. As his lips trailed down her neck, her body trembled with pleasure and delight...

(Source: Tulle Kiss Bunko, translated)