Initially, the personalities of the twins seems to be energetic and fun-loving. The only difference between is the way they make their hair. Aside from that, in the beginning they can also be compared to Maru and Moro from xXx Holic due to their parts of their personality, the fact that they are twins and the habit of talking at the same time.
But later, on it is revealed that this was all nothing but an act. They are supposed to be criminals, and ended up with a role in the 'Main Cast' because 'he' (possible Fumito Nanahara) could keep the things off their record, or even wipe them off since otherwise, it was hard to get a job.
In the end, they are revealed to be mean and treat Saya like a monster and they don't share any closeness either. When they actually did die, one twin puches back the other twin in an attempt to escape with their life. Which comes to prove that they were nothing but a bunch of selfish crooks.