Kantai Collection

Kantai Collection (艦隊これくしょん, "Fleet Collection", a.k.a. 艦これ, KanColle) is a Japanese browser-based Card Battle Game by Kadokawa Games initially released in 2013, in which the player is an admiral (JP:提督, teitoku) managing a fleet of Moe Anthropomorphized warships from World War II.

The task of these "fleet girls" (JP:艦娘, kanmusume, often shortened to kanmusu and also translated as "shipgirls") is to fight the mysterious "Abyssals" (JP:深海棲艦, shinkaisei-kan), a fleet of (what appear to be) corrupted fleet girls and sea monsters who have driven humanity back from the sea.

The admiral's job is to direct their operations, supplies, and repairs, and somehow find time to manage the furniture and marry one of the fleet girls (or more than one).

The game itself is pretty thin on story and background, but there are multiple spin-off mangas, audio dramas, and a Twelve-Episode Anime with a sequel movie set in its world (or worlds based on its central concept, anyway).

"Sendai: You need to think a little about how she feels."
 * All There in the Manual: The game itself provides little exposition, requiring those who want to know more to turn to supplemental materials. Unfortunately, some of said spinoffs are set in Alternate Universes with different mechanics, which makes things confusing.
 * Bribing Your Way to Victory: Most resources can be obtained in-game by sending the fleet out on missions, but they can also be purchased instantly in the shop. A very few items like rings or extra unit and equipment space can only be bought with real money-acquirable DMM Points. Downplayed, however, in that there is no gacha for paying players to throw money into in search of high-tier units or equipment that give a decisive advantage over those who don't splurge.
 * Buxom Is Better: Bust size (and overall age) seems to correlate with ship class and firepower. Destroyers look middle- to high-school aged, cruisers high-school aged or recently graduated, and the battleships start 'mature' and go from there -- compare the fast-battleship Kongou to super-battleship Yamato... There are a few inexplicable deviations, though, like (not so) Hidden Buxom destroyers such as Hamakaze, Naganami or Ushio and short, flat carriers like Ryuujou and Taihou.
 * Canon Fodder: What are Fleet Girls? How do they fight?  Where do they come from?  Are they the spirits of the warships themselves, summoned from some 'ship afterlife', or are they regular human girls or women who are somehow found to be 'reincarnations' of these ships?  How are they related to Abyssals?  The game itself is silent on the details, and while several spinoff media have contradictory views on it, Kadokawa have not endorsed one over the other.
 * The opening narration of the anime adaptation indicates that fleet girls are born human and somehow obtain the spirits of the warships later.   Fleet girls and Abyssals fight on the surface of the water (appearing to "skate"), and carrier girls launch their airplanes by firing their ranged weapons (e.g. shooting an arrow which turns into a wing of aircraft).
 * In the manga KanColle: Someday as the Seas turn Calm, the fleet girls skate as they do in the anime, but aircraft are launched 'conventionally' from their flight decks.
 * In the manga KanColle: Bonds of the Wings of Cranes, fleet girls are the reincarnations of warships, summoned (essentially) from the moment of their sinking.
 * Some of the 'one-shot' manga anthologies depict fleet girls as being warship-sized giants!
 * Creator Provincialism: Of course, most of the ships are Japanese, and many of the seasonal events are based on campaigns from the Pacific Front of WWII (which raises some hackles in other countries...).
 * Critical Existence Failure: Averted. At medium/moderate damage, some abilities like closing torpedoes or carrier participation in the shelling phase are disabled and a penalty to damage dealt is applied. At heavy damage, an even greater penalty is applied.
 * Featureless Protagonist: The admiral is almost completely undescribed and uncharacterized.
 * Filk Song: "Kongou Bongo", a song that uses the tune of "Civilization" but is about an Admiral's love for Kongou (instead of "the Congo").
 * Final Death: A sunk shipgirl is gone for good, and any equipment she had on her too, if you don't have certain rare items equipped when that happens. As a minor mitigation, no friendly unit can go from full health to sunken in a single battle; the worst that can happen is being brought to heavy damage, in which state she will stay for the rest of the battle regardless of how many further attacks are thrown her way, and it is only if trying to advance to the next battle that the risk appears.
 * Friendly Fandoms: With Arpeggio of Blue Steel (the Winter 2013 event included several characters from the anime adaptation Arpeggio of Blue Steel -Ars Nova-) and World of Warships (there's more than a few players who get Japanese warships because of this game or its anime adaptation, and players who use them are likely to encounter catchphrases from the anime in chat).
 * Historical In-Joke: Lots of the girls' quirks are based on their service or history. For example, Kongou was built in England (and then rebuilt in Japan), and so has an affinity for tea and often sprinkles her speech with Gratuitous English.
 * Level Up At Intimacy 5: Marrying a fleet girl lifts her level cap from 99 to 155, reduces her fuel and ammo consumption, and improves several of her minor stats (e.g. luck, evasion, and scouting).
 * More Friends, More Benefits: There's no limit to how many partners an admiral can have (although each ring after the first costs real money).
 * Luck-Based Mission: You can have well-levelled and well-geared units, but none of that will matter if they miss, only score scratch damage, aim at the wrong targets (especially at boss nodes, where sinking the enemy flagship is the only thing that matters), or catch a random Critical Hit from an enemy.
 * Moe Anthropomorphism: The fleet girls appear to be human, but wear "rigging" which bears features of their 'ship-selves' (e.g. smokestacks and turrets). Other major accessories or distinctive features may be worn (e.g. headbands with distinctive radar masts or antennas) or carried (e.g. flight decks).
 * Off-Model: Many of the fleet girls look different in the anime than their in-game CGs, mostly those originally drawn by Shibafu (which includes several major characters, e.g. Fubuki, Akagi, and Kaga). Tropes Are Not Bad, however; Shibafu's art style is sometimes disparagingly called 'potato' (their faces look round and featureless), so most fans consider the changed faces an improvement.
 * Politically-Correct History: To be fair to Kadokawa Games, most of the atrocities of World War II were committed by civilian governments or ground forces, rather than navies. However, the inclusion of the submarine I-8 (whose crew did commit war crimes) raised more than a few eyebrows overseas, as do the seasonal events which revolve around recreating historical or planned (Japanese) naval campaigns of World War II.
 * Voices Are Mental: Averted. In the "Hiei's Curry" radio drama, Maya switches the Kongou sisters' headbands around while they're in the showers, and while they swap mannerisms when they come out and put them on, their voices stay the same.
 * What the Hell, Hero?: In the anime, Fubuki pushes herself almost to the point of destruction, hoping to impress her admiral (who had previously put her into an oddball mixed fleet, and then broken it up once she got it into shape) and earn her remodel. She is almost fatally destroyed in battle, but barely survives.  When she wakes up, with Mutsuki tearfully embracing her, her first question is whether her final attack had hit the Abyssal she had (almost fatally) charged.  Mutsuki shouts at her to take better care of herself, and flees crying.  Sendai comments disapprovingly: