Mashiro-ke Complex!

The Mayo family consists of four Kyodai: the eldest son, Jun; twins, the second and third sons, May and Kon; and the eldest daughter, Natsuki.
They attend the same high school. Their parents are wandering abroad, but the kyodai, led by older brother Jun, help each other out and live together day by day.
But...these Kyodai actually have a secret...