World 5/5-3

Tips

 * All nodes, except end nodes, are night battles only; there's also a submarine node if you have any slow ships in your fleet.
 * Sinking the Flagship Wa-class transport ship at the boss node will lower the boss gauge by 20%. You need to do this 5 times to clear the map.
 * 2DD, fast ship, and high torpedo stat (for night battle) is recommended. You can also use an all submarine fleet, but it will often be directed to J instead of Boss.
 * Taking advantage of night battle equipment (Star Shell, Searchlight, and Type 98 Recon Seaplane (Night Scout) ) is recommended and Sparkling your ships should be considered as well.
 * Unless you need S rank for drops, you do not need to destroy the Hime nor the submarine and you can bring a light fleet to deal with the Flagship Wa-class transport to clear the map instead.
 * Although the S rank on boss gives you decent drops on this map, it is highly advisable to just disregard the S rank boss drop here and settle for A or B rank. All the drops here can be farmed later in the next maps which is easier to S rank for the boss.
 * There's a gold submarine in the boss node. A possible tactic is to bring 1 CL flag with heavy ASW gear and 5 DD, enter battle in Line Abreast formation to deal with it quickly, get less damage from enemy ships, and thus focus on night battle. This fleet composition is the most resource efficient and can often succeed. Try Double Line or Line Abreast on pre-boss nodes to absorb enemy cut-in attacks better.
 * Another possible strategy is to run 2 Fast Battleships, 2 CA(V), and 2 DD. This has a high chance of reaching the boss node and can get a lucky kill on the Wa-Class but costs more fuel, steel, and ammo. Make sure not to equip bomber seaplanes such that your ships do not target the SS. A variation of this is to replace 1-2 CA(V) with CLT, but 2 CA(V) should be used for the final form because of the changes in the boss composition. If using CAV equipping them with 2 seaplane bombers and 2 seaplane fighters will allow you to obtain Air Superiority while clearing the bar.
 * A possible strategy is to run 3 CLTs, 1 CA(V), and 2 DDs. This is the most efficient with highest Attack power/torpedo and lowest possible encounter rate (C-D-I-K).
 * Both enemy and ally submarines do not have increased evasion during battles STARTING at night, i.e., hitting them is as easy as in any day battle.
 * Akitsu Maru can gain air superiority at boss node with 2 Reppu or Shiden Kai 2 at maximum proficiency, and air supremacy can be achieved with 3 Shiden Kai 2 at maximum proficiency. This, still enabling artillery spotting for your fleet. This is the base of another method :
 * You can try to bring Isuzu Kai Ni + Akitsu Maru + 2 DDs + 1 CA(V) + 1 (F)BB(V) and go Double Line at boss node, this way, you can gain Air Superiority / Air Supremacy, enabling Artillery Spotting for your side, Isuzu Kai Ni with full ASW can even sink the enemy submarine as soon as possible, allowing your DDs to attack other ships at night => More chance to sink the Flagship Wa-class transport ship.
 * Keep in mind that is a slow ship, so you will nearly always go to node B, but with both Searchlight and star shell activated, there is a good chance that enemy submarines won't even perform Cut-Ins and you can get away with no damage.
 * This composition heavily relies on, she needs to be in good health condition in order to sink the golden submarine at boss reliably. If she is moderately damaged before reaching the boss node, may as well retreat.
 * You can try to equip one Sonar for each DD to help sink the submarine
 * You can bring 2 CA(V)s instead of 1 CA(V) + 1 (F)BB(V), but you will almost always go to node F (Increase one more battle before going to boss node) so it's advisable not to do so. Without 2 CA(V)s, you will either go D-I, D-E (low chance) or D-F, meaning there is a good chance that you will go D-I and only fight 2 battles preboss => No ammo penalty at the boss node.
 * With boss support expedition's help, it's possible to sink the entire enemy fleet.
 * It is also possible to sink the flagship at the boss node with only the help of the the Support expedition but it may require some luck.
 * Another possible tactic is to send a fleet consisting of 4 or more SS. This composition is very resource-efficient, but the drawback is a lower chance of going to the boss node from I (25%). This lower chance is often offset by the higher rate of reaching the pre-boss node without suffering critical damage and allowing you to clear the stage in 20-30 sorties on average (depending on ship levels). A SS fleet tends to go to node B, where you can avoid damage by getting a D rank.