Phase 1/World 1/1-5

This is the first map which has branching rules, the first map with a boss HP bar requiring multiple completions, and the first map where you can face Flagship and Elite enemies. The map is filled with only submarines unless your fleet composition is wrong and you go off-course.
 * You are required to sink the boss submarine 4 times to clear the map.
 * Since it is an Extra Operation, clearing this map is not required to continue onto World 2.
 * Clearing this map rewards a Medal and 75 ranking points. At the start of each month, the boss HP bar will reset, allowing the rewards to be obtained again (if it doesn't reset, refresh the game, or get a new API link if you're using one).
 * The enemies on the map are scaled to your HQ level, which means that the enemies will rank up when you hit a certain HQ level. Nodes power up at levels 40 and 80.
 * drops on the boss node (Node I) for those who are HQ80+. She only drops if you currently do not have, meaning that you cannot get duplicates this way.

Beginners

 * This map is a good place for players with HQ level below 80 to level their DDs and CLs. For details, refer to the leveling guide.
 * Defeating the boss on this map will give you a large amount of HQ experience. If you don't want to inflate your HQ level and thus your enemies, then consider retreating on C node.
 * Recommended composition: 1 CVL 1 BBV 2 CL. This will guarantee that you reach the boss node. You may replace any number of CLs with DDs if you wish.
 * Taking more than 4 ships will not allow you to reach the boss node.
 * 1 BBV is recommended since it can equip Seaplane Bombers to hit subs while allowing you to enter the second shelling phase.
 * 1 CVL is recommended since it can equip Saiun to prevent T-cross disadvantage (Red T), which can make killing the boss difficult without good ASW equipment.
 * It's possible to replace the CVL with a CAV or AV, but it's not advisable to do so without good equipment. An AV can equip Depth Charges, a CAV has better armor and can equip Seaplane Bombers to hit subs, but neither of them can equip Saiun to prevent the occasional Red T.
 * Putting Sonar and Depth Charge on same ship will get 15% ASW power bonus (doesn't stack, one depth charge and sonars is the usual setup).

OASW

 * Isuzu Kai Ni and ships with ASW of 100 or greater (or in the case of DEs and Taiyou Kai/Kai Ni: 60 and 65, respectively) will allow you to perform Opening ASW attacks, making the map much easier.
 * Recommended composition: 3 OASW-capable DD/DE + 1 CVL/AV/LHA. Ideally: 3DE + Taiyou Kai (Kai Ni)/ Zuihou Kai Ni B. This setup trades the BBV for a DD or DE, reducing the resource consumption while disabling the second shelling phase, but also allows preemptive attacks that disable the enemy subs before they attack, working as if it was an extra shelling phase. You can swap up to 2 DDs for CLs. Using CTs or CLTs is also possible.
 * Drop CVL/AV can be used (that is, dropped level 1 ships), up to two times without resupplying. Generally, this doesn't affect boss, boss S rank, and bucket rates. The cost is around 50 fuel and ammo for full sortie. More drop ships (DD and CL) also can be used, reducing resource consumption even further (Satsuki Kai Ni and 3 drop ships will cost around 10 fuel and ammo per full sortie); however, this will affect boss and boss kill rates (possibly down to 50%).
 * CVL/AV/LHA range can be increased to medium/long by using OTO/SCAMP (will attack first in the first shelling phase after the OASW phase).
 * For DD/CL/CT/CLT use one Type 3 Depth Charge Projector, and 2-3 Type 3 Active Sonars or Type 4 Passive Sonars. Generally, CVL/AV/LHA equipment don't matter, you can use boilers, bulges, normal ASW equipment, or default equipment if drop CVL/AV is used.