Feels weird calling these official art even though they are by the manga's author.
If Yabuki Kentarou started making full on sex art or doujins for To Love-ru would we also call those official art?
Technically, yes. Also Tsugumomo regularly have this kind of nude even inside the actual chapters, the only thing that makes it retain the 'ecchi' label instead having 'hentai' label is there's no onscreen depiction of characters having sex.
I have yet to see any of the manga but I have started the anime series recently. Have been enjoying the sneaky convenient censor moments they have like with loli Kiriha in the bathroom. If the manga is more daring, as is often the case, I may have to make a point to check out a few chapters.
I'm already quite smitten with Kukuri, she is adorbale as is her way of speaking. Her little childish fights with Kiriha remind me of Kobato and Maria from Haganai.