What exactly is an otome game?
The short definition of an otome game is a video game that features a female main character who can romance/date male characters as a part of the story. It is written as 乙女ゲーム in Japanese -- meaning Maiden Game -- and sometimes shortened to otoge.
Some sort of romantic plot should be taking place throughout the story and should be one of the main -- if not the main -- driving forces behind the plot of the game.
The protagonist (referred to as the MC or main character) must be female. If a game has the option to have a male/female/or gender-neutral MC it can still be considered an otome as you're able to play a female MC.
The available romantic routes should be a majority of -- if not entirely -- male love interests (LIs). It's possible for an otome game to exist that has one or two routes involving women characters; although generally in Eastern otome games these are "friendship" routes and don't culminate in a truly romantic ending in which the MC and LI get together. If you're interested in otome games that also feature a female LI, I recommend checking out Western OELVN's made by indie devs. There are plenty that feature at least one female LI. If the game has a majority female LIs then it would generally be considered a GL (girl's love) game.
It needs to have character sprites with changing facial expressions, CGs (computer/color graphics), and backgrounds. A CG is generally a fully illustrated piece of artwork that represents what's happening in a particular scene. These are usually strategically placed when there's something romantic happening between the MC and the LI, although they also are sometimes used during comedic scenes instead. The character sprites should change as the LIs talk to react to one another to show some feelings. Some otoges have a lot of sprite variations, including outfit and pose changes, others only have a few.
There must be choices the player makes that determine the ending one gets in the game, and there should be multiple endings per LI. Generally, these involve selecting how the MC will react or respond to things the LI is doing or asking. Sometimes there are stat-raising or other mini-games that also affect the outcome of the story. The amount of endings per LI can vary depending on the game. Generally, you would expect a game to have a best or good ending and a bad ending. Some games feature no bad endings and simply have a best and normal ending instead. Some games have a gratuitous amount of bad endings that can abruptly end the game if you make the wrong choice.
If a game fits the above criteria it's an otome game. There are also joseimuke games which are games that have a female target audience, but don't always involve romance. Many gacha games with primarily or all male characters (such as Twisted Wonderland) are joseimuke games. As there's no romance nor does the "player" character have a set gender, TWIST and other similar gachas are not otoges.
This is a very strict definition of otome games, but I don't have strong feelings about others referring to joseimuke games as otoges. However, I'll be using the above definition when selecting games to play and when I update this website.
You can find otoges on mobile, PC, Switch, PSVita, PSP, and a few select ones on PS4. I will be primarily playing Switch games with an occasional PC game thrown in as I do not own either portable PS system to play older games. If you'd like to try Switch games, you can find them for sale frequently on Amazon. Publishers (such as Aksys) will also sell them directly from their website. You can pre-order these games from BestBuy, Gamestop, and other large retailers that sell video games; however, they rarely keep these in stock long-term. If you don't pre-order a game, generally Amazon or the publisher will become your only option to purchase a Switch game after a few weeks. You can occasionally find pre-owned otoges at Gamestop, although admittedly many otoge players are collectors and rarely sell their games -- this is also because they become harder and harder to find as time passes!