While there is fanservice as early as when Ido started his coloured manga, I think we all agree that Colorado's introduction marked the series's official step into hotter and sexier area, where the fanservice is actually addressed or used as the punchline. This Colorado mansion arc alone has several pages of Pola in her panties in various angles, Baguettebotes going full bdsm, and multiple Colo-chan ass shots. And then later we got Kuro Kashima/ Katori with the fundoshi stuff, and the Hornet ramen mini-arc.
Not complaining though, as this Pola panel alone shows that he can pull off an excellent mix of fanservice and humour.