Piracy: ꜱᴀɪʟ ᴛʜᴇ ʜɪɢʜ ꜱᴇᴀꜱ

Hi everyone. As the title says, I'm looking for a method to download manga on smartphone and then read it with a proper offline reader (any suggestion is appreciated).

Example: I've been reading comics (downloading them on the smartphone and then reading them with "Perfect Viewer" app) for years and I would start to read manga also with a similar solution.

I prefer to download them on the smartphone (and don't read it online) because I don't have always a decent Internet connection, and when I can access to that I use that to download as many comics I can.

Thanks in advance for all your help

EDIT: Thanks for your help, I'll try Mihon and Kotatsu