Mastering Manga with Mark Crilley: 30 drawing lessons from the creator of Akiko https://www.amazon.com/dp/B006WUD10S/ref=cm_sw_r_cp_apa_YjREBbKPVP282
Since you have a specific interest area in mind, here's a link to a cheap Kindle book about how to do that. The artist is on YouTube, so you don't have to blindly drop three bucks.
I'm not good at drawing at all, but with the help of this eBook, I can draw a pretty decent manga face in a few different styles.
Well, they're still awful, but much better than before.