"Please be my big bro..." Get ready for a chaotic rom-com between an overprotective office worker with serious sister issues... and the obsessive guy she introduces him to! One evening after work, Aoto comes home to find his little sister introducing her university senior, Tachibana. But Aoto, being way too overprotective, goes overboard trying to keep Tachibana in check. In frustration, Aoto's sister storms out of the house, shouting, "I hate you, big bro!!" Drowning his sorrows in booze, Aoto ends up being comforted by the very guy who caused all this drama—Tachibana. As they talk, Aoto starts to think, "Maybe he's not such a bad guy..." and drunkenly leans on him for support. But then—bam! Tachibana suddenly pushes him down and kisses him! Wait a second... was he after Aoto this whole time?!