What do you mean devices?

Basically, small little movements and licks that get used to spice up longer chord progressions, maybe something to fill a bridge, or put a twist on something familiar.

Modal Mixture

If you read the page on chord progressions, I mention how the third and seventh are the most important notes in a chord. Take the Dminor7, the third and seventh notes are F and C. Within Cmajor the only other 7chord that holds these notes is the Fmajor, an excellent substitution, but what if we look outside of the key? That's when we do some modal mixing... I'm not going to explain why it's called that, maybe later.

For a major7 chord, if we raise the first and fifth note, we get a minor7 chord one half step up. Example, Fmajor7, with the 1 and 5 raised becomes F#minor7. And obviously, if you take a minor7 chord and lower the first and fifth, you get a major7 one half step down. Because they share the third and seventh, these two chords will funtion in the same way. For example, instead of a 2-5-1, you can play a b1-5-1. Now, I can sense your neurotic itching, your drug addled shivers, the veins in your neck about to explode. You're a salivating, twitching mess waiting for me to tell you how Hare Hare Yukai ends, so here I will oblige you: b3-2/5-1. You: 2/5? What the fuck are you talking about?

Suspended Dominants

Dominant chords work because of the interval the third and seventh create, the tritone, right? Wrong. Tell the third to fuck off by raising it a half step or lowering it a whole step. Now you have a sus2(lowered) or a sus4(raised) chord. Now it's an anime chord, you rearrange the notes to make a minor or a major chord in the right hand with the root of the chord in the bass. Example for G dominant: Dminor7 over G, Fmajor7 over G. The little slash symbol means over. So Hare Hare yukai goes from the b3 to a 5sus to the 1. Cute twist.

Back to modal mixture for a sec

The other one you may want to know is the b5half diminished. It's just the 4 chord with the root note raised by a half step. This way you can do a 2-5-b2 progression to the 4, and this gets used whenever there's a sad part of an anime song, because the happy resolution has been defiled, and the half diminsished is pretty spooky/sad sounding. What songs often do next is they'll resolve it to the 4minormajor7(Minor7 chord with the 7 raised by a half step) chord, which is like sadness resolving to even deeper sadness, then they'll typically go to the 3 and do a 3-6-2-5-1 thingy. Also the b7dominant is modal mixture I guess, if you read the last article you know it's a substitution for the 5, so something you'll hear is a 2-5 from the 4minor to the b7, and then surprisingly it resolves up to the 1. Neat.

On that b5, there's a progression you''ll hear, it's in THANATOS and THIS KIND OF LOVE by Shiro Sagisu, and the end theme to YOSHIS STORY, it goes 2-5-3-6-b5halfdim-7dom-3-6-2-5-1, the reason why this sounds nice I figure is because the 3 to the 6 is the same movement as the 6 to the 2, and a 2-5-3-6 starting on the 6 would have that "3" as the half-dim. Also people play the 3minor chord as a half dim to add some unexpected sadness, but in JPOP specifically its a bit rarer than the b5. An example of that would be a 2-5-3halfdim.

Parallelism

Playing the same chord shape around the keyboard sounds surprisingly good, you're not playing in any scale but it just works, so people will use parallel movement as passing chords. For a 3-6-2 you can go 3minor7-3bminor7-2minor7, or for a 2-5-1 you can do 2minor7-2bmajor7-1major7.

Chromatic Lines/Line cliches

Chromaticism just means moving around by half step, Take a major triad and raise the top note by semitones until you get to the tritone from the third(6 half steps away) Now you have a dominant. Now do the same for the bottom note. Now take a minor triad and raise the top note by semitones until you get to a tritone away from the third. Now lower the bottom note. Four little progressions made just from moving 1 note.

Picardy third

Instead of ending your progression with a minor chord, raise the third of the chord and get a dominant instead. 4-5-3-6dominant. Bach liked doing this, and so does Jpop.

Tritone sub

Look at the third and seventh of a dominant chord. Might that interval exist in another dominant chord? How curious. I wonder if they're substitutional...

Ikisugi

Flowers in Chania

This is a meme chord that gets used in some neat ways. It's a voicing for a dominant chord, you play an augmented triad a tritone over your root note, and resolve it down like a tritone substitution. In this way you can create a false resolution from a dominant, example being G dominant to GAug/Db instead of C. I don't speak Nihongo but I think Ikisugi means like edging or blueballs as slang or something. Delayed gratification.

Here's a funny vid about it, probably the reason why it's a meme: https://youtu.be/0MqlNBcUw5I?t=204

b6

You can do a 2-b6dom-5-1, or a 2-b6dom-5-b2dom-1. You're basically doing a tritone sub for the 5 chord. The jazz standard(I'm sorry for giving an example that isn't JPOP) The days of Wine and Roses (at least it's a japanese singer!) Goes from the 1 to the b7dom to the 6 dom, same concept.