YMMV / O.N.G.E.K.I.

• Fan Nickname: "ω4" (Omega 4) is often referred to as "w4" in English-speaking circles.
• Play the Game, Skip the Story: This game is very story-heavy compared to other arcade rhythm games, and your cards have affection levels that give you side stories with the characters. There are players who ignore all of this and play O.N.G.E.K.I. strictly as a music game. This is helped by the game having a score system based strictly on player performance, Technical Score; mobile gacha games are infamous for not having such a system, causing new players to scratch their heads over why their perfect performance was awarded with a mere C rank (and, in older such games, not even recognized as an all-perfect, just a full combo at best)^note This is likely because score being tied to card power encourages people to roll the gacha (and spend money for such). O.N.G.E.K.I. gets away with having both scoring systems because it's an arcade game that you pay to play for each session, so whether you roll or not, the arcade and the publisher get your money..
• Scrappy Mechanic: Some songs with Lunatic charts only have Lunatic charts, which is problematic as Lunatic charts are usually in the upper end of the difficulty scale, thus screwing over players who want to play these songs but don't have the skill level to play on Lunatic. Did you want to play the Shoot 'Em Up songs, for example? Hope you're good enough for level 13+ charts and above!
• Shocking Moments:
  • That this game, alongside maimai and CHUNITHM, have a collaboration with Arcaea is already enough, but then Sega revealed part 2 of the collaboration, which includes "Red and Blue and Green" and a Lunatic chart for it, which nobody expected due to it being an April Fools' Day song in Arcaea.^note Although, Lunatic-only songs are primarily Gimmick Level, and the colours in this game are red, blue, and green, so it's not completely out of place.
  • bright MEMORY's "Memories of O.N.G.E.K.I." event was going through the seasons, but completing wasn't expected to add another, final stage, including a hidden boss obtained by getting perfect scores of 5 different Level 15s, the outright ending theme of the game, and a Lunatic mode boss stage that's not only the first original Lunatic and first Lunatic 15, but seems designed to be outright impossible. Then, after that, you unlock another hidden final stage, featuring the first and only Level 15+ and an upgraded version of the Lunatic boss.
• Spiritual Successor: This game feels like a take on Konami's SOUND VOLTEX. The game uses a vertically-oriented screen and uses a combination of buttons to hit notes and an analog device to follow tracks and features a gacha system, similar to SDVX. Furthermore, the hold notes seem to alter the sound of the background track when hit.
• That One Attack: "Fly to the Leaden Sky" seems about typical for a chart of its level (14), but then you get to the part that the song preview doesn't tell you about (but which you probably saw coming if you've played Battle Garegga before): The "Stab and Stomp!" section. The notes are mostly done away at this point and the only button-based actions you now need to take are holding down the red and blue buttons, but the bullet patterns amp up and become replicas of Black Heart's infamous patterns, including the sweeping spread pattern that, similar to its presence in its source game, can easily kill careless players who are not used to the Bullet Hell aspect of this game.