Seishun Otome Banchou!

Due to her scary face and penchant for fighting, high schooler Mihane Hirata is known as the “Killer Demon.” But, she’s actually an earnest 16-year old in love … While trying to get closer to her beloved Toma, the cutest guy in her class, she accidentally confesses her love to him! Not only that, but before Toma can respond, Mihane suggests that they try dating for three days … ?!

(Source: Kodansha USA)