K Manga, available on Android and iOS. It's surprisingly overpriced compared to all of its competitors. I don't mind paying coins to unlock manga, but for just a few chapters on K Manga, I could get a whole month's worth of Viz Manga, Shounen Jump, Mangamo, Azuki.co, etc. Hell, I could probably subscribe to all of them combined (although I wouldn't have the time to read more than 2 of those, honstly) for the price of keeping up with a handful of series.
Based on my experience, K Manga is the worst deal in paid manga right now. Anybody that gives you a $5 or less monthly sub (it's as low as $2 for Viz Manga, and $3 for Shounen Jump) gives you a lot more content for a lot lower of a price.
Even Crunchyroll's manga section, which has always been a clustf** and has gone downhill even moreso lately, now that Kodansha's pulled a bunch of content off of it.