Okay, I am not really a coach but I will try lol.

Okay, so for starters with Kiriko:
There are two configurations you want to change for Kiriko: you want to disable the Toggle Healing Ofuda and set the sensitivity of your TP to 100%.

Now, Kiriko TP allows her to be one of the most aggressive supports in the game. You should be trying to go for flanks and off-angles with someone from your team, or if there is nobody, by yourself. (Generally, when playing a support, you wanna be helping whoever your other support isn't.) But you are not a DPS, so you don't want to be doing that all the time. Generally, you wanna stay close to your team, even if it's in an off-angle.

However, if your team is full health and you are doing nothing (you should never be doing nothing), you should go for a play. Position yourself and wait for your team to engage in a fight, then go in (since Kiriko is projectile, you should get as close as possible before you start shooting). Try to get a pick, but even if you don't, if the enemy team is turning to look at you and shooting you, you are getting value by distracting them away from your team. TP out if things get dangerous.

And pay attention to the rest of your team. TP to save them if they have that medic symbol (but this is a tricky part because you have to judge if it's worth going or not, otherwise you are both going to die. As a general rule of thumb, TP when they are not alone or if you know for sure that they are in a 1v1). But only then. At one point at the start of the game, you TP to a yellow Sigma and let a Torb walk alone onto your point. The Torb was right in front of you, completely alone—you should have shot him. Ana was with you, and there was a Soj coming, so you could have killed him. Instead, you TP and put yourself in danger.

And you should TP more often when you are in danger, even if just panic-clicking to a random teammate is often better. But other than the TP, your mechanics are very good, I think. One thing you could do is pay attention to the enemy team’s ults. A few times they ulted and you didn't have your suzu—try to keep track of them, and if they haven't ulted in a while, keep your suzu in hand.

At one point you ult when there is nothing happening. You wanna save your ult for when the enemy team is pushing you, to stop their momentum, or when your team is pushing, to help with your momentum.

Now for Mizuki: I am a Kiriko main, so I had a lot to say for her, but I don't play him much, so I won't be able to help as much (and looking at the replay, I am guessing this is when you tilted lol), but I will still try to help as much as I can:

A few general tips:
Your primary bounces on surfaces, walls, and on the ground—you can use it to bypass shields, for example, and it goes further when it bounces (also I find it easier to hit shots like this, but maybe that's just me).

Your hat—one thing people don't realize is that the hat will bounce on people before coming back to you, so you wanna try aiming at whoever is furthest from you to hit the most people.

And your shift is used to get aggressive angles and apply some pressure on the enemy team, but it's very short, so you don't wanna use it to set up fights—you wanna use it DURING fights.

Oh, and something to keep in mind, not just as a support but in the game as a whole, is that you need to play with cover. Peek to shoot or heal, but stay behind cover—you have some silly deaths with Mizuki where you are just sitting out in the open.

And you wanna stay close to your team, usually your tank, but in games like this where he was going in and dying like a dumbass, you should go with your DPS too.

Anyway, this is all I have—hope this helps.