Only found this series just now. Honestly, I'd have been happier if it'd been a pure one-on-one romance instead of a harem, but personally I don't think any of the girls so far are that bad.
One thing though: Ikuta is no tsundere. Tsunderes are hateful and dismissively condescending, as if they're personally offended by things the MC says, or does, or even his simple existence. Ikuta doesn't show any of this. The worst temper she shows is a small pinch at the realisation that she's not the only runner in the race. If you want to give her a "dere" title, I believe the current term for this type of character is "tease-dere". In essence, she's trying to pull something between Takagi and Nagatoro. And from what the boss says, it sounds like even her slacking off isn't real, more like something she does to get his attention. Still an annoying thing to do, and I can completely understand that, but it's not like she sees him as a convenient tool.