Manny is someone who has never been the type to get any attention from anyone. He was always reserved and kept to himself, so when people saw him like this, they thought he was weird and never approached him.
In fact, Manny has never had a problem speaking to others. If people get to know him and talk to him, they will be charmed by his positive attitude and outlook on life. The same happened to Adam.
From the moment Adam laid his eyes on Manny, he could tell he was a good person, and was impressed by his attitude towards his own averageness.
The point is that because of Manny's outer appearance and behavior, he never got attention from anyone, so now, having two beautiful girls before him, showing off their deep cleavage right before his face.
With little to no experience when it comes to matters related to the other gender, Manny couldn't control his little friend downstairs. Luckily for him, the girls' attention was not on him but on Adam.