Tate vs Hoko! ~Saikyou no Imouto to Muteki no Osananajimi, Koi no Yuuwaku Daigassen~

"Who the hell are you?! Don't lay a hand on my Minoru!!" "Huh... M-mine... You mean my brother?! Th-that's... impossible...!!" A chaotic scene unfolds before my eyes. The two girls fighting are the complete opposites. One is my frail, helpless little sister, Mamori. The other is my glamorous, assertive, caring childhood friend, Saki. For some reason, both of them seem to be in love with me. Being pursued by both my little sister and childhood friend at the same time, what kind of romantic comedy manga is this?! ...Anyway, I can't leave things as they are. I have to skillfully fend off their advances... No, that's impossible! What kind of ending awaits my love for them...? [Translated from DLsite]