I gave this game three tries across separate months in this year and could never get past the tutorial on each try. This is gonna be a long ass post because I wanna drop my thoughts on this game that no one cares about somewhere. This game is incredibly fascinating because "blatantly inaccessible" does not even begin to describe it. Every single aspect of this game is a filter on some level.
For the first filter, there is no real overarching story. The base concept is that that you play as a human from the real world possessing an android fighting for a military rebel organization in the 23rd century in underwater Mars. Your goal is to achieve universal peace in three years (there's a calendar system like in gunpa- I mean persona) or else every planet ever nukes each other and existence is over. Sounds like fifty SF story ideas put together but this isn't even the beginning of it. One would expect more of a story but there isn't one. The entire game is 80+ hours of talking to the 36 NPCs (some you have to unlock) on your battleship. The cast is equally as strange, it ranges from a dolphin in a cyborg suit to a giant octopus that's named "Ika" to a seven foot tall early 20th century Italian mafia named "Iron Sovereign". The strangest of them all however is this one kid who is just, a normal boy from our universe and that's his entire thing.
The second filter is that pretty much everything that's normal in other games is way overly detailed and has something stuck to it. What I mean by this is that, this game is tied to "realism" like no other. Aboard the battleship, whenever you want to use the elevator you have to actually wait for it and a lot of the times other NPCs are using it. I've never seen a game where you have to painstakingly wait at least a full minute or two for an elevator just like you would in real life. Some aspects are cool, for example you cannot offer the one Arab character alcohol because Muslims don't drink. Same thing with the underage members of the ship (you start being able to drink with them once they grow older). There's no fast travel or anything like that either, you have to walk across this gigantic submarine every time you want to go somewhere. Another thing is that, with Gunparade March I remember thinking that the AI in it felt incredibly realistic. Now I am glad that they did not feel TOO real because goddamnit this game goes way too hard. The AI in Kenran Butousai act just like real people, in that you can't even talk to them when you want. Aboard the battleship, pretty much everyone is busy with something and they all have their individual moods that you have to pay attention to. This doesn't sound all that special but consider this, if let's say an NPC is busy most of the time they will straight up not even respond to you. Not only that, there is a really detailed memory system where if you say you will go do maintenance for your mecha, the other NPCs remember that and go "Weren't you going to do maintenance? Stop being lazy and get to work." It gets really overwhelming especially with so many people on board, there's also like a dozen dialogue options for every single one of them and they always give some sort of new answer just like in Gunparade.
Oh yeah, the mecha. That's the third filter, besides the social aspects which are 95% of the game there's parts where you fight your enemies in your robot called the "Round Buckler". I can't even begin to describe the battle system, just skim through this clip here https://m.youtube.com/watch?v=NzKHCxP5V6M&t=535s .
Lastly, this game is a direct sequel to Gunparade March and there's a ton of returning characters. This being said, you won't even recognize any of them unless you know a lot about the overarching lore in the franchise and half of them aren't even actually the same people but alternate universe versions of them. In general, the game is so strange to me because it's like they saw everything people liked about Gunparade and decided to do the exact opposite. There's like a billion things I'm not going that into, such as the fact that the calendar system is actually tied to your real time too. Every time you save, dates pass by in the calendar. For example, if you save on August 7th and return to the game on August 14th three weeks pass in game. Not only that, but the game also counts your real hour play time too and that decides which ending you get. IIRC for the best ending you need to have over 50 hours in the game. All in all, I think this game is very cool and it's kind of lame that it's so unknown because I feel like some people would love it. But, I can't really score it and I never even got past the tutorial because I do not find it fun. If you love blatantly inaccessible games that are meant to be as overly complicated as possible this is your game. Either that, or this game is meant for people actually from the 24th century like in game. Oh and also, there's zero voice acting and this game has more menus you constantly have to read than probably any game ever AND there's a bunch of ship announcements that are in real time that you have to keep track of so... grinding a ton of Japanese is a must.

SeaBed is the best story I've ever read. It is beautiful, honest and cathartic; however: this game is not for everyone. Firstly, it's a visual novel. Secondly, while not being as long as some other characters in the VN medium (erm, Umineko), it is really slow and filled with very rich and very detailed prose — more akin to what you'd find in a classic paperback novel than your typical VN.
To me and to other people who love the game, these are very positive qualities; to others, however, they are such a bold detriment that it's cause for dropping the game completely. It's also very mundane, in traditional SOL fashion (think less Hidamari Sketch and more Yokohama Kaidashi Kikō). And again — some people love it, others loathe it.
If, however, you like your Slice of Life, you like your romance (or just Yuri in general) and, above all else, if you enjoy letting yourself sink into the vast, dreamlike sea, being absorbed into the world and its characters and its very, very enchanting prose, then I'm sure you'll love it. SeaBed is a profound tale of love and loss and grief — and of coming out stronger on the other side. It is uncompromisingly honest, incorrigibly vulnerable, and, as previously stated — really, really, outstandingly beautiful.

SeaBed made me cry for like 20 minutes straight while trying to read it through tears. I've never really read anything else quite like it, and it seems to me that it's truly a shame that it isn't widely regarded as one of the best visual novels out there. Sure, part of what makes it so unique – the extremely slow pace, and a story that is mostly interested in looking at its characters through everyday conversations and the mundane details of their lives – is somewhat off-putting to a lot of people; so it probably makes sense that it's not that well known.

However, by the end of the game I personally felt like there was hardly a wasted moment in it despite how slow and relatively light on plot it is. All the time spent on characterization and building up the central mystery of the game was, to me at least, absolutely essential for the story of SeaBed to be so affecting and end so strongly. It really is a beautifully constructed visual novel, that's well worth reading even if its narrative structure is different from anything else you've ever read.