This looks like an adjective, but it's actually a noun. This word is the same as the kanji meaning: vow (or oath).

Who did you make a vow to? It's your chica (ちか)! You swore an oath to her, pledging loyalty, support and companionship. Try to picture a chica you would exchange vows with. In fact, it doesn't have to be romantic. Maybe you both just vowed to read more books this year.