Having two same person in a family is not a great life for Yang Yoseob. He has a twin, identitical twin that the eldest named as Yang Yojun. They look alike and it is very hard to tell the differences between them.

A strong bond, same personalities and figures make their family members, realtives and friends 99% misunderstood of which one is Yoseob and Yojun.

During their childhood, Yojun is much brighter and active than Yoseob which is more to passive and 'mute'. They have a non-relative hyung named Yoon Dujun that is a decade older than them.

Dujun was 15 when he realized of his ual preferance and fell in love with one of the twin. He told the eldest about him being gay for a cute boy and got  a hard objection for almost two years from his side. Dujun moved to Japan and left the twin for four years before he came back and claimed his right on the boy.

However, lot of things changes yet he is still thinking the boy he loves is same as before.

Brief:

Yang Yoseob is the hyung while Yojun is a dongsaeng. The thing that make them different is their hairs' colors. Yoseob tends dyed his hair while Yojun is pure black.

Dujun is a secret agent for Korea Security System and age is 28 while the twins are 18.