I should be starting a thread on YS IX, of which I've played around 10 hours, but instead I'm opening a thread on a Switch game I've bought yesterday and played for about a fifth of Ys' time.
Susume!! Mamotte Knight is the third (IIRC) in the series of games were your chosen hero has to slain a seemingly endless wave of enemies while defending a princess who, if hit enough times, will cry so hard to erase the whole level. The game has been developed by Yuzo Koshiro's own company, Ancient, featuring NES style graphics (but luckily no flickering) and sounds. Upon booting the 3DS game (Minna de Mamotte Knight) you need to blow on a virtual cart, here in Susume!!...to be honest I don't really know. I think you're tuning the channel but I'm not entirely sure.

The game has changed quite a bit from Minna: your task is still to defend the princess from monsters with the same heroes as before (Warrior, Amazon, Mage, Archer, Ninja, an old man riding a fake horse) plus two (a Prince/Princess, not entirely sure, and the Miko seen in Minna), but now the princess' castle is on thread. So, instead of defending a static point, the whole game is a giant escort mission. The mission ends when the princess' castle reaches the enemy's castle and destroys it by constantly ramming into it.
You can still grab the princess and move her around, but the castle won't move without her and from what I've played there's no reason to move her out.
Stages begin with the camera panning around the map to show the castle's path and the various obstacles, like coloured gates that need a key to be opened, barriers that have to be smashed by the castle, blocks that will go away after you defeat a certain amount of enemies, switches to change the castle's path, or holes your hero has to get in to let the castle continue.
So far enemies have been the same as Minna, with the same attacks and spawn points. You can no longer wander around a stage freely, you can't get very far from the castle, and there are instances of treasures that can only be reached when the castle has progress far enough along its path. When the castle reaches a stop, new fortifications will spawn around the stage to make your life a little easier.

Despite using the same heroes as in other games, their skills and progression have been completely changed. Everyone has a fixed skillset, and you can purchase different sets in the shop (run by the two same fairies from Minna, by the way). Heroes can no longer level up during stages, but the princess still heals them when nearby; you can only level four stats (health, attack, quality of spawned fortifications, princess' health) after a stage, and those improvements are gone after completing a mission (a group of four stages). Before beginning a mission you select three heroes (you can pick duplicates) that act as lifes: once one is defeated, the next takes his/her place, and lives/heroes are replenished at the next stage.
While heroes do have different stats and basic abilities (the Warrior is stronger than the Archer, but the Archer can hit from afar), what really tells them apart are the skillsets. Every hero has a staple skill from previous games (like the Amazon's spinning chakras...or whatevery they are called), but then not everyone can reinforce existing fortications or move them, and among the basic skillsets, no one can build new ones. This makes heroes more different from each other and limits how powerful some were in Minna, but the Amazon and the Miko appear to be a notch above all thanks to a good mix of defensive and offensive options.

Stages last five or so minutes, so a mission is wrapped up within half an hour. The missions I've played so far aren't hard but there are two difficulty levels hidden behind some yet unknown requirements.
The game supports online multiplayer (but you need Nintendo's paid subscription) and local multiplayer with up to four people. In the options you can change voice sampling between 8-bit and 16-bit (although the 16-bit sounds a bit too clear...let's say 8-bit and modern), and a small array of other options (volume, vibration, tips). For some reason there's no way to get back to the title screen from within the game, you just quit Susume!! from the Switch's menu; the game saves automatically, but I can't hide it felt quite strange...modern games give you all the wrong habits. Oh well.

To promote Susume!! Mamotte Knight, Ancient released a NES game I still have to try. And I don't mean a companion minigame to whoever downloads Susume!!, I mean a NES ROM file you need to play on an emulator or through an Everdrive. This bonus is available in English and Japanese, while Susume!! for now is only in the latter language.

If you've like previous Mamotte Knight games (named Gotta Protectors in the west), Susume!! will still entertain you, although I would have like new enemies right from the start...I know orcs and minotaurs are a staple of the series but more enemy types are never a bad thing.