Other than that this is your typical ship-waifu collecting game where SSR will always be proven to be superior in every aspects (and yes, this has been a thing when I talked to peeps playing in CN as I also used to play CN version) so bear that in mind.
Equipment system is similar to Azur Lane so you know what to expect tbh, equipments are based on rarity and they're all upgradeable. Missions to get exp and all the good stuff opens everyday, which makes it better because you don't have to wait for day x to get the thing you're looking for.
Unlike CN version, the main mission has more missions you need to clear before you can do X-1 ~ X-4. To make it more "fun", these missions have auto disabled and certain missions will force you to go on a specific route so you need to minmax your fleet composition very early in game.
And then, we have to come to the biggest issue and its generosity; gacha. Every other games hace their own gacha rate but for Blue Oath..... I can say it's pretty bad, but there's something interesting about it. For every new banner you can roll for X times (20 or 30, kinda forgot) and you'll get one guaranteed SSR without having to pay extra cost, there's a box on the right side of the banner for you to press.
What else? I have nothing to say other than "if you're an Azur Lane players looking for Kancolle Arcade clone with mechanics that you'll feel you're at home then this is the best one you can get"
Edit #1: editing my review after a more thorough gameplay, some aspects of the game were changed in JP version, eg. expeditions which is missing from the game.
Edit #2: another edit as I see people are complaining over rarity gap and the abysmal rate of gacha (while obviously only playing for several days)