Koi ka Yamai ka

"Something is wrong with my body..." Tetsumaru is the personal bodyguard of Ageha, daughter of the Harukaze conglomerate family. He is a faithful servant, but recently he has been suffering from a problem: when he sees Ageha, his heart leaps out of his chest. This must be a symptom of an illness! Palpitations, shortness of breath, tremors in his arms and legs... In order to protect the young lady, he can't give in to his sickness!!

(Source: Kodansha, translated)