SHE IS THE BEST WING WOMAN
Misaki would be, but she don't know how to help with romance considering the uh, her whole backstory. So Hiyori was Hiruto's next best option.
I kinda have a wing(wo)man tierlist.
(Note: I may have some of these personalities wrong. The spotty translation hardly owes well to proper character voice.)
Hiruto- Very awkward and stiff about it, yet would be straightforward and not rely on any stupid schemes.
Erika- 50/50. Either she'll use the perfect tactic from one of her favorite romance novels, or she would intentionally try to sabotage any attempts you make.
Hitomi- Would be a proper gentleman (/gn) in wingmanning, if a bit grand with the romantic gestures on your behalf.
Hiyori- 10/10! Best wingwoman!
Justin- Not very good. Has all the romantic skills of a cat offering a dead bird to its owner.
Kotori- Would probably do only the sweetest of gestures, both figuratively and literally, with full confidence.
Mayu- Ehh, can't see her wasting her time with romance, yet I'd imagine she'd be as straightforward as Hiruto/Nozomi.
Misaki- See your own response.
Rikka- Probably would be a Justin-tier wingwoman.
Rintaro- Probably knows all about romance, but would be remarkably creepy about it, driving your crush away in the process.
Rion- In a weird way, I believe his self-deprecation would serve well in making you look good to your crush. Then again, if you paid him to do it, he would probably be a wingmanning master.
Satoshi- No clue how he would wingman, unless he used some weird puzzle or riddle that only he could solve.
Shoji- A Hiyori-level wingman, and would upload his attempt on the internet too!
Ukyo- Would probably be like Hitomi in his wingmanning. A total gentleman.