Love Is Indivisible by Twins.

Jun Shirosaki’s love life takes a wild turn when he finds himself caught between the Jinguji twins—his childhood friends who are as different as night and day. Rumi, the older sister, pairs a boyish charm with a maiden’s heart, while Naori combines girlish looks with her deep love for otaku culture. As feelings grow and confusion mounts, Jun must navigate this unexpected love triangle next door.