HUNTC-101 My two sisters, who are complete opposites in appearance and personality, are fighting over my big dick! They're completely different, but they have the same taste in dicks! My harem life where I'm popular with my sisters

My older sister is a bit of a sadist and a bit of a nerd. By the time I realized their true nature, my dick was already completely locked on! I'm in a relationship with these two sisters, and they tempt me at every opportunity in my daily life! Finally, when they reach the age of puberty, a battle breaks out over my dick! To be honest, they're both cute and sexy, so I can't choose! Seeing me like that, my two sisters force me into a threesome, saying, "Whoever makes their brother cum first wins."