Mysterious Twins

The protagonist, Kazama Shota, has a Nordic family move into the vacant mansion next door. Shota falls in love at first sight with one of the same-aged male and female twins from that house. After becoming friends with the two of them and several years passing, when he enters middle school, he finally confesses his feelings and gets a yes—but there's a problem. It's because the one who became his lover was the boy...