DOA is actually a quite good fighting game series, in the style of Virtua Fighter, but with heavy emphasis on counterplay, using a system where strikes beat throws, counters beat strikes, and throws beat counters. Usually a big series feature is tag play, but the most recent one (6) oddly dropped tagging and went solo-only. 5 had a great tag team survival mode where it'd load the next opponent in the background while you fought their partner, so you could have a fairly seamless fight through the entire sequence. Another frequent feature is gimmicky arenas, with area changes and things that can trigger from hitting someone into the right place.

It's also made by devs who prominently exploit their characters to downright absurd degrees, releasing and rereleasing waves of often obviously cheaply made fetish-wear DLC hoping people will collect outfits and whatnot. They always start a version of the game out talking about how this time it's a serious fighting game and not just fetish trash, and then inevitably they start pushing the flood of outfits and swimsuits they have piled up, which gets annoying even if you don't want it, because they'll dress the AI stupidly in your fights whether you want it or not, instead of doing something sensible like letting you turn off or substitute outfits you don't want to see. Yet, for all that, it really is a good fighting game under the hood, even if they did just ditch it wholesale for a while and make volleyball fetish resort games instead.

They also took a big vocal stand against selling DLC characters in fighting games when someone else started doing that, talking about how it was wrong to have to pay to train against opponents and they swore never to do such a vile thing. Of course, they were selling their own DLC characters before that edition of the game was even over. Shamelessness is definitely a series staple.

The last couple editions have changed to a F2P model, where you can play some characters for free (I think a few are fixed while others rotate periodically), and either buy only the ones you want to keep unlocked, or find the "real game" DLC and buy that (plus any missing "extra" characters). So, it's at least a very easy series to try out nowadays.

This thumbnail tells you everything you need to know about DOA:

Best summary I can give: 3D-movement fighting game, very much based around having three heights of attack, and a few ways you can guard moves based on their height, as well as react to your opponent's guard.

It's mostly known for sexualized characters, some of which are visually on the "younger" side, and a very complex, DLC-driven, gacha-based method of unlocking other costumes for its roster. It shares a universe with the Ninja Gaiden games, so a few of those characters like Ryu Hayabusa appear as more than just cameos.

It's a fighting game for lonely manchildren.