Something tells me the other dude was part of the plot. The girl told him she liked the dude, the other guy being friends with both, decided to help out. Unfortunately the MC is dense as fuck and really bought into the story, so much he's still not fully convinced it was all a lie.
Judging by the flashback at the end, it was at the very least the other guy's plan to get the two together. Not quite as sure about the girl being in on the plan.
This is one of those chapters that rewards readers
who pay close attention to the clues and details.
Pages 5-8:
Otsuka is very comfortable about initiating
sex, and she seems to be quite skilled, too.
Page 9, Panel 4: "...and buy me dinner after this."
That's precisely the sort of extra tip
an experienced JK Girl would ask for.
(https://en.wikipedia.org/wiki/JK_business)
Page 10, Panel 2:
Otsuka spots a fat pigeon. Note the "cat smile."
Page 16: "What a rumor... Let's make this clear...
I don't do this with just anyone, okay."
In other words, the rumor is partly true.
Otsuka does sell sex, just not to any
slob who asks.
Page 16, Panel 5: "I happen to have a lot of cash."
Probably from selling herself to older men.
Otsuka likes Marui, but business is business.
She intends to keep him poor, but she'll also
keep him on the hook by picking up the tab
once in a while when he's broke. Clever girl.
Ah yes, the usual 'false rumour' type story. At first when she mentioned 'it'll cost you extra', I actually thought for a moment it was true, but I guess she was really just playing along with the rumour?
That ending though...Well, I guess maybe he's a bit too dense to figure it out despite her pretty much spelling it out for him, so she's just going to keep going along with the rumour that she's a slut so she can continue this relationship with him?
When she mentioned that someone might hate her or she turned them down, and it showed his friend in the club...Makes me wonder if he also liked her but she already liked our protagonist? But even then, if he started the rumour or if he just told it to our protagonist, he was still technically quite the wingman?
I'm not sure what to think of her saying she has a lot of cash though, makes me wonder where she got it if she wasn't...selling herself.
The chapter is full of clues that suggest Otsuka
is probably a JK Girl who rents herself to older
men. That's why she has a lot of cash. See my
long comment elsewhere for more details.