Very strong oki assist that allows Tatsuya tons of freedom. Monster train (6S) covers a large portion of the screen and Tatsuya can cover Rusian very well with 236X allow him to get across. Tatsuya can also let the opponent kill Rusian and go for a hard punish into a full combo. The combo points where you will be calling Rusian 5S are anytime the combo uses 236AB or j.214AB.
While mostly a combo and neutral too, Dokuro allows Tatsuya to do meterless assist combos making her a strong pairing to strengthen two things Tatsuya does well. The other function of Dokuro is giving Tatsuya another anti-air which is very useful while in trump mode as he does not have extremely good ones. 5S can be used any time Tatsuya is in the air to bring the opponent back on the ground. This notable allows Tatsuya to get both hits of j.214X as it pushes the opponent in the right distance for 5S to hit. 6S will be used less, but any grounded string that uses 236, 6S can be called during it for a bit of extra damage.
Strong in both neutral and allows for setplay. 5S (baumkuchen) is a situational anti-air helping cover the spots where Tatsuya’s 5B cannot, but they also allow you to safely approach or as a combo extender. Cats are a great oki tool that allows Tatsuya to safely use 236X follow ups to continue stagger pressure, or provide multiple tick throw/high-low mix ups. Pressure aside, it also minimizes your opponent's movements keeping them pinned down. Mashiro will normally be used for oki but sometimes you need an extra bit of damage and 5S is a good way to extend. Anytime j.214AB is used to go from the air to the ground, 5S can be used to keep the opponent in hitstun, allowing for a continuation. Similarly to Dokuro, sometimes a meterless extension can be gotten for a low to the ground air to air conversion with the use of 5S.