As soon as I laid my eyes on this game, I recognized an element I saw in another mobile Konami game called "Contra: Return". In fact, they are three specific elements:
From there, it was a simple task to deduce one thing -- the game has "Energy". The little lightning icon, on Contra: Return, is like "stamina" that you use up by being deployed on different missions, tasks and other events. If you run out of Energy, you cannot play the game and must refill it. On Contra: Return, this is done by wasting coins, diamonds or -- you guessed it -- real money.
It has also come to my attention via a trustworthy source that these diamonds are the best currency, but you get TOO few of them at a time to properly buy stuff with them, pretty much requiring you to use real money if you want to get good equipment, for instance. I can definitelly see this all amounting to where the microtransactions come in, but there's more.
This game has something else that is also present on Contra: Return, but that I speculate works differently here (for worse):
This game has a timer. On Contra: Return, this timer is ever increasing saving for specific missions, but I think here this is not the case. While an static image doesn't show whether the timer is counting up or down, I chose this image for a reason: The boss' HP is almost full, and the timer is at 9:22. This suggests that the battle has only just started and is counting
down. All other gameplay screenshots containing a timer have it always above 8 minutes, something that occurs when you must get some nice screenshots fast right after beginning to play any given mode.
So, yeah, you understand it right: The game has Energy and a timer, suggesting that if the time is up, you have to start the "mission" again and waste more energy, until you can no longer play at which point you waste this game's version of "Diamonds" to buy more energy, which will eventually require you to waste real money.
Sans the "energy" and "real money" parameters, this would be close to how Harmony of Despair does it per level, except that Harmony of Despair is not meant to be as casual as a mobile game, hence why this game has not shown numbers above 10 minutes for the timer up until now.
Depending on your perspective, this could be bad news. The timer working like that also implies the game is not a "metroidvania". If you have multiple missions and stuff like that, you can't possibly hope for a competent metroivania experience done in 9-10 minutes. But this is just the time for a proper (maybe if somewhat shorter) linear experience, such as the one seen in Adventure Rebirth. There's a screenshot showing Shanoa on a screen that appears to have multiple paths, and we HAVE seen Adventure Rebirth pull that also despite being a linear game. Also, the fact that this timer appears to be counting DOWN, not UP like in Contra, tells me that Konami wants you to be wastin' those dollars as soon as possible.
Also, a little sidetrack: This Wyvern appears to have around 47,200 HP. By adding up the damage numbers on screen, you get 1475. Then, by taking the sliver of damage it has taken on the bar and pasting side by side until the end of the bar (32 times), you arrive at 47,200 HP. This game is no stranger to huge numbers, as you can see on Simon's "55,631" HP bar; If I'm right here, then the countdown is even more corroborated (meaning that they DIDN'T take 9:22 minutes to deal that one tiny sliver of damage to the Wyvern).
Finally, the screenshot of the three currencies comes from this screen:
It's a music select screen. On all other screens these currencies are nowhere to be seen-- why would they show up on this screen but not on the apparent HUB-world one? Well, that's because I suspect you have to buy the soundtracks with these currencies. The player here has bought them all, so that's why you don't see any numbers on the tracks.