Turns out it was fungus. Read around and I suppose it's ringworm. But how is that possible?? I've not idea, it could've been my house, but never had I seen it with the first 3 cats. I read that she may have already had it, and could have been trigerred by stress, due to new environment and presence of the other cats. What ever it was, it better go away soon.
So instead of vaccination, she was treated for that, they cleaned the area and prescribed some pils and cream to apply, they said it wasn't so bad that she didn't need to be injected for that. Apparently the thing spread fast so it probably had only been a few days.
YUMIEKO could actually still be vaccinated, but because of her condition, I didn't want to have her vaccinated, which may add more stressor to her. Further more, I got the impression that they were surprised to know that she's already 3 months, but if I say she's 3 months then she's good to go for the vaccination. So I decided not to, after all, her size was kinda small.
As for MICHIKO, he was there for the walk. I didn't want him vaccinated either, coz I wanted to save the trip for their future boosters, so I want them to have their vaccination on the same date.
They came in one carrier, so to avoid passing on of the fungus (which may have already been passed on anyway) on the way back, MICHIKO was in my bag which he pretty much enjoyed.