Happy to see this thread still alive.
Apologies for the low quality pic, it was screenshotted from a 720p Nisekoi episode on a 1080p screen.
Also, most of the FetiColle series (by Jitaku Vacation/Ulrich) features delicious armpits - of note is FetiColle Vol.1.
SadPanda link -
https://exhentai.org/g/994139/4021d9995a/Non-SadPanda link -
https://nhentai.net/g/178513/