Why subbu?

Why has subbu been reintroduced into the show its just doesn't add up at all. He was the one who left ishita and he didn't seem that bothered about her in earlier episodes. All of a sudden he's here and super rich for a dentist with this mysterious old lady. If they have introduced him because KP will be going on leave for his wedding then they could have have said he's taking Rome away for treatment or something to do its his health problems.