This is my first ever guide, so please feel free to comment if I miss something or list some sort of misinformation. Thank You.

Keiko is by far one of the most unique charators in this game due to her trap based playstyle, and her trusty pal Q. All of Keikos specials are done by Q, and his health bar is her meter (Yes he can be damaged). Its also important to note that, Q can attack at any time (even while Keiko is blocking, grabbing, or performing any normal). This makes Keiko very hard to deal with when she is up close. Butt though she may sound OP, she does have her weaknesses (which I will get to by the end of the guide).

Throughout this guide, I will use the following terminologies...
s-a ---------- Press "A" while standing
s-b ---------- Press "B" while standing
c-a ---------- Press "A" while crouching
c-b ---------- Press "B" while crouching
j-a ---------- Press "A" while jumping
j-b ---------- Press "B" while jumping
qcb-a ---------- Hold "A" while also holding down and back
qcb-b ---------- Hold "B" while also holding down and back
qcf -a ---------- Hold "A" while also holding down and forward
qcf -b ---------- Hold "B" while also holding down and forward
a+b ---------- Press "A" and "B" at the same time
grab ---------- Press "B" and forward or back, while close to your opponent

I will devote a later section to strategies, butt four now Im just going to list her moves...

Normals
Like all other characters Keiko has 6 Normals.
s-a
---a typical jab.
s-b
---a decent poke.
c-a
---meh, dont use it (unless you really want too)...
c-b
---Keikos rangiest normal. Also hits low
j-a
---Keikos best jumpin and air2air.
j-b
---a hefty crossup. can be used as an air to air (butt not recommended)

Specials
As I said above, Keiko does not perform any special moves; Q (her cat) handles those himself.
qcb-a
---Q turns into a flat, low hitting carpet. breifly launches opponent
qcb-b
---Q quickly turns into a large verticle stalk. can be used as a anti-air. launches opponent
qcf-a
---Q does a quick forward moving attack. launches opponent
qcf-b
---Q reels back, and comes forward with an overhead that knocks down. very slow start-up
a+b
---Q quickly explodes and is unuseable for the rest of the current round. Is a very consistant anti-air, and launcher

Movement
Keiko does not have a foward dash, like many other characters. Instead Q will perform a (somewhat fast but punishable) forward dash.

Keiko has a pretty interesting neutral game...
While it may seem like a good idea at first, sitting back and letting Q do all the work is an easy way for him to become roadkill. As you can tell by the bar under Q's lifebar, all of his actions have alot of recovery frames (even his dashes). Though he is not vulnerable during the start-up and active frames of his moves, he can be punished during his recovery frames.

It is most optimal to play Keiko and Q at the same time. Keep Q safe by having Keiko protect him during his recovery frames and vice versa.
While in neutral try to use...
--- alot of qcb-a, as a defensive option (can also anti-air)
--- qcf-a to move in on your oponent
--- qcf-b to claim some space against your oponent (can also anti-air)
--- j-a to protect Q

Generaly, the idea is to force your opponent into the corner where your combos and damage are the most consistant. Lastly be very mindful of Q's health, Keiko is near useless without him. Prioritize his life moar than getting damage on your opponent (Unless your oppenent is almost deabt -_-).

Keiko has the potential to do alot of damage when Q is within close proximity.
Typically, try to forward dash while jumping in (to keep Q within range). When you get those plus frames, follow up with one of the options below (or create an option if you want).

While midscreen

s-b --> qcf-a --> c-b
ends in a knockdown. 4 total hits including jump in.
block confirm off of qcf-a, and walk up for another mixup (s-b or grab)
You may want to walk forward a bit to get the final hit.

grab --> qcb-a (or qcf-a) --> s-a
you may not get the last hit all the time, due to Q's position. may do 4 hits.

s-a --> s-b --> qcf-a --> c-b
simple frame-trap to catch your opponent teching or mashing.
the first hit is meant to be blocked.
block confirm off of qcf-a, and walk up for another mixup (s-b or grab)

s-a --> s-a --> a+b --> c-b
hit confirm off of the s-a's to get 5 hits (including the jump in)
very consistant anywhere, but you sacrifice Q

While in the corner

s-b --> qcf-a --> c-b
ends in a knockdown. 4 total hits including jump in.
block confirm off of qcf-a, and walk up for another mixup (s-b or grab)
Much moar consistant in the corner.

grab --> qcb-b --> c-b
very consistant in the corner (though qcb-b doesnt have much horizontal reach)
4 total hits and knocks down

s-a --> s-b --> qcf-a --> c-b
simple frame-trap to catch your opponent teching or mashing.
the first hit is meant to be blocked.
block confirm off of qcf-a, and walk up for another mixup (s-b or grab)

s-a --> s-a --> a+b --> c-b
hit confirm off of the s-a's to get 5 hits (including the jump in)
very consistant anywhere, but you sacrifice Q

While Keiko does not have any sort of Invincable move, Q can easily keep her opponent at bay. Remember that Q can perform any action at any time (regardless of Keikos current state). Try to keep Q close to you on knockdown and force your opponent to back off. Keep in mind that Q is really your only defensive option, without him you're very open to punishment.

After reading all of that, you might be like "Oh, shes super cheap and OP", while I assure you, she is not. She has several weaknesses, she especially has a very hard time dealing with zoning. Tenchi is a HUGE problem. Tenchi's fireballs force Keiko to take the hit for Q (as to not let him die). Not only that, but if you jump over a firball and punish Tenchi, your potential damage output is lowered since Q couldn't jump over the fireball.

From my expeirience, this matchup is her worst, and I've developed a few strats to keep Q alive. While in this matchup, perform alot of special moves while in neutral. Since Q is invulnerable during the startup and active frames of any special, he can avoid fireballs like this. Specifically use alot of qcf-b, since it has alot of start up.

Anywho. as you play her youll learn even moar about her unique play-style. Get used to improvising, to get consistant damage from your hit confirms. Have Fun and Gg's ^-^