This drama is unnecessary, but realistic as well cuz there's still common sense in it. I really like this blondie not only she didn't became a hindrance between the two of them she also went her way to clear up the misunderstanding that would probably last for a few chapters that would result with MC and FMC break up. MC didn't even have to explain himself since she resolved the problem right away.
Anyways talking about MC's D(no homo) since we haven't seen the actual image of his D the way the blondie described his D and rating it as an SSS tier D... I'm guessing MC's D is probably between 10-11 Inches long and his girth size is probably between 6-7 inches. I can say he's truly massive. It's safe to say that his D size and stamina(since he can last for 4-5 rounds) is more than enough to know the FMC is truly safe from NTR.