IM@S – Deep, Deep Blue (Y/B) [07/28/2025]

The wonderful mermaids of Diamond Diver◇ have recently received even more support through the release of the newest premium booster for Idolm@ster. In celebration of the premium booster, we have crafted a deck profile here that shares a take on an updated version of an old combo given new life through some additional cards, that of the Deep, Deep Blue combo. I would like to note that this deck is focused on facilitating Yayoi’s combo rather than the individual members of Diamond Diver◇.

This build is focusing on the original Idolm@ster; therefore, no Million Live exclusive characters can be used in this deck profile due to Bushiroad’s restrictions. I am also aware that all the cards suggested are allowed to be used with Million Live; yet, we will leave it to the players’ decisions on where to take the deck going forward and whether they would like to use original Idolm@ster cards or to tap into the Million Live potential.

Thanks to the inclusion of the new 2/1 Yayoi, Deep, Deep Blue has gained some more support to push advantage and get ahead on resources in the mid-game. 3/2 Yayoi from an older Million Live booster is a restander combo with her climax that also shuffles back up to three cards at the end of her attack from your opponent’s waiting room, giving her a second encore type of swing. 2/1 Yayoi combos with the same climax to refund you a stock from the top of your deck while also letting you salvage a copy of 3/2 Yayoi.

Pairing with Yayoi, Chihaya is highly recommended. Her modular early game plus provides you either option to perform a Minami effect or salvage a level two or higher character from your waiting room. The second ability in particularly is great as a way to secure our 2/1 Yayoi in the mid-game.

As our combo primarily requires stock, we’re going to have to prepare early on while looking for ways to push our stock advantage. Both Chihaya and Ami here perform the same ability as you can tuck a card from hand into stock when they both enter play. Chihaya has a double trigger ability while Ami gains potential soul when she attacks if you mill a climax off her ability. Either or, both are great options to push damage while transforming hand into additional stock.

Some other ways to generate stock start with Azusa to the left. Azusa is an interesting card that works two-fold in our deck. Firstly, when damage dealt during her battle is cancelled, she can go straight to stock. Conversely, if she’s reversed, she’ll go to memory, giving us a little bit of compression. Lastly, she has a level zero yellow shift ability, letting us filter her with our clock. Overall, she provides a little bit of everything, and since our deck is based in yellow and blue, she’ll be a good addition. Yayoi cheering allows us to clock ourselves to check x based off of our number of other characters on stage, potentially nabbing us a climax we need and milling our deck. More importantly, when our opponent plays a climax, she can go straight to stock, empowering our late game.

While 0/0 Chihaya and 0/0 Mami will burn our hand quickly to generate stock, we need to be able to maintain pressure and resources. In order to do so, these two profiles are great in order to keep our hand and field healthy. Azusa is a Zero Two profile, sacrificing our cards on field to regenerate hand from the top of our deck with a bit of luck. Yayoi is a Clean Cut profile, perfect for pushing our front row cards to the back to be reused later during our next turns. These two also share an innate synergy where you can sacrifice your backrow with Azusa to open a slot for the clean cut Yayoi’s effect.

During our opponent’s turn, Yayoi is an anti-change backup that sends our opponent’s cheated cards to stock. Mami is a Leafa counter, perfect for fixing our hands and digging us closer to a cancel.

Normally, I would move into the final section of the post, but I want to make a slight exception here. When thinking about deck-building, I came across the dilemma about considering putting red into the deck. The thought process here was, while red would provide great flavour incentive as I could put the other members of Diamond Diver◇ to push more into the a sub-unit theme, red cards provided little to assist Yayoi’s finisher as a whole. There were some generic cards here and there that could be slotted into the deck, but that isn’t the purpose of this deck profile.

Yet, there was a single card that felt quite flavourful and genuinely rewarding to the deck profile’s play-style. And in that sense, that card was none other than this 1/0 Morning Greetings event. Featuring Yayoi on its cover, this card would freefresh both your and your opponent’s decks, giving Yayoi’s finisher a higher chance of reducing the amount of cancels and increasing its kill potential (in the right circumstances of course).

Two standouts in the colour that I want to draw attention to are that of Hibiki and Yukiho here. Hibiki is more straightforward in terms of value to the deck as she is a stock charger if you have a climax in play, stocking the top card of your deck on swing if it is level one or higher. Yukiho is a bit more nuanced as she generates value is a more sneaky way. Yukiho is a spawner profile that brings out any level zero character from your waiting room for the cost of a single discard. Normally, this wouldn’t be too impactful were it not for the fact that we can easily spawn out Azusa or Yayoi and make use of their static abilities. Both are great as they contribute to colour requirements for Yayoi’s event.

Some other game pieces to consider for this deck profile begin with Yayoi playing with her frog toy. Yayoi is a standard Fukaziroh profile that is also a level zero stock reverser, perfect for punishing your opponent’s board while cycling you into a potentially useful card. Ami is a drop searcher that also grants an enormous amount of burst power on swing to one of your characters. Chihaya performing is a search Riki profile that also has a top check rearrange ability on play that works well in conjunction with cards that care about your top of deck like 1/0 Azusa. 1/1 Makoto is a bottom deck Adachi profile to deal with all unfair threats and can be spawned from your waiting room at the start of climax phase for its cost. The Futami twins together (Mami) is a redraw profile that also gives you the ability to check three and add a card to hand.

Deep, Deep Blue’s addition of the 2/1 Yayoi profile and a bunch of quality of life cards give the deck more power and a nicer feel to play. May the gentle mermaids of Diamond Diver◇ be with you.