Let's take a look at their Legion units shall we?
Shura Stealth Dragon, Mantrakongou
[ACT](VC): Legion 20000 "Shura Stealth Dragon, Daranikongou"
[ACT](VC): [Counter Blast (1), and discard 1 card with the same name as a unit on your (VC)] If this unit is in Legion and your opponent has 4 or more cards in his/her hand, you may pay the cost. If you do, choose 2 cards from your opponent's hand, and bind them face down. Choose one of your opponent's rearguards, and bind it face up. During the start of your end phase, return all cards binded by this card's skill to your opponent's hand.
[AUTO](VC): When this unit attacks a Vanguard, if there is another unit in the center column, this unit gets [Power]+3000.
Shura Stealth Dragon, Daranikongou
[AUTO](RC): When this unit attacks a Vanguard, if your Vanguard is in Legion, this unit gets [Power]+2000 and "[AUTO](RC)]: [Soul Blast (1) When this unit's attack hits a Vanguard, you may pay the cost. If you do, choose up to 2 cards from your opponent's bind zone, and place it into his/her drop zone" until end of turn.
Well, well. I kinda expected this from Bushiroad. Although Nubatama rarely gets support, when they do, it's really good. These 2 cards add on to their gimmick of playing with the opponent's bind zone very well. The Legion effect can be achieved very easily, considering most Legion decks would have large handsizes, and having very few cards in hand is kind of Nubatama's "thing".
The G2 Legion mate combos with the G3 very well for high pressure. The Legion skill would place 3 cards at maximum into your opponent's bind zone, then the G2 can attack the Vanguard to pressure your opponent to guard. If he/she doesn't guard, that's an instant -2 for him/her, which is obviously a bad thing. For even more pressure, the starter from BT13 can be placed behind the Vanguard. Here is it's skill:
Stealth Beast, Kuroko
[AUTO] Forerunner (When a unit of the same clan rides this unit, you may call this unit to (RC))
[AUTO](RC): [Soul Blast (1)] When an attack hits a Vanguard during the battle that this unit boosted, if you have a <<Nubatama>> Vanguard, you may pay the cost. If you do, choose up to 2 cards in your opponent's bind zone, and put them into the drop zone.
By using this unit and placing it behind your Vanguard, it adds even more pressure. Even if you attack with the G2 Legion mate first and it fails to hit, this unit boosting the Vanguard's high-powered attack would add alot of pressure to your opponent to guard, or it's -2 to them instantly.
Overall, I would say I'm impressed by these 2 units, as not only do they go along with Nubatama's old gimmick, they are very pressurizing units when used correctly in a well-built deck. To help you, below is a decklist I came up with. Feel free to follow it or share your opinions in the comments :)
4 Shura Stealth Dragon, Mantrakongou; 4 Shura Stealth Dragon Kabukicongo
4 Shura Stealth Dragon, Daranikongou; 4 Stealth Dragon, Kokujou; 3 Stealth Beast, Tamahagane
4 Stealth Beast, Minjakure(pg); 4 Stealth Dragon, Dreadmaster; 4 Tempest Steath Rouge, Fuuki
2 Stealth Beast, Hagakure; 4 Stealth Dragon, Kurogane(critical); 4 Stealth Fiend, Mashiromomen(stand); 4 Stealth Fiend, Otsuzura(draw); 4 Stealth Fiend, Zashikihime(heal)
Starter: Stealth Beast, Kuroko
Kabukicongo acts as a back-up plan when your hand size goes too low, and you can't afford to use the Legion skill anymore. This way, he still pressurizes your opponent a lot with his LB4, and the help of the G2 Legion mate and Kuroko.
Kokujou is basically a staple in every Nubatama deck. Because of the cards in the bind zone, Kokujou will power up significantly when you use the Legion skill or Kabukicongo's LB4 skill. Tamahagane can be combo'ed with the Legion skill to set 4 cards in your opponent's bind zone, a nice even number for Daranikongou and Kuroko's skills to go off.
Dreadmaster is just a pressure unit for your opponent to guard, since you would very easily have less cards in your hand than him/her. Fuuki helps to build up the soul, and at the same time combos with the Legion skill to make 4 cards in the drop zone for Daranikongou and Kuroko's skills to go off later.
Hagakure is just fun to use as it makes your opponent use up his/her hand even on his/her turn, since you would very easily have less cards in hand than your opponent(unless he/she purposely decides to use up his/her whole hand on RGs, which would leave him/her quite defenseless later).
There is no other option than rainbow triggers for Nubatama, but it works well nonetheless. Stands can be used to restand pressure units on the field(like Daranikongou), criticals add to pressure on the high powered units on the field(like Kokujou), and draws help to maintain hand size at a decent level to maintain defense.
All in all, Nubatama is a very fun deck to use, but tricky as you need to know when to time your moves right. Feel free to share your opinions on these cards and the decklist in the comments below :)