A quick lineart tutorial for anyone who's just starting out like I did.

https://s6.postimg.cc/t9bgg8bup/step1redline.png

First I sketched some really messy redlines as a guideline for my lines. A lot of stuff wasn't added in the red lines, and were added in the final sketch. I used the marker brush from Medibang Paint Pro.

https://s6.postimg.cc/v14fb52xd/step2opacityredlines.png

Lowered the opacity on the redline layer for my next layer so lines won't mess me up but I can still see them.

https://s6.postimg.cc/db2qq44s1/step3overlay.png

On a separate layer with the Pen Brush, I drew over my redlines but added some things to it. Notice how I don't completely follow the guidelines. Those are just a base sketch you could say.

https://s6.postimg.cc/55koryo8x/step4smoothlines.png

I hid the redlines layer and edited the official lines a bit more.

Step 5

https://s6.postimg.cc/s719xpvm9/step5finallines.png

Final step, with a separate layer for credits and I added some final detail to it.