There are several swords that are considered the best in Blox Fruits Second Sea. The best sword for Second Sea depends on the players preference and playstyle. Here are some of the swords that are considered the best in Blox Fruits Second Sea based on the search results:

• Saber V2: This sword is a good choice for players who are just entering Second Sea. It is a common sword that can be upgraded via the Blacksmith NPCs and enchanted via the Dragon Talon Sage to deal extra damage and gain unique abilities.

• Shisui: This sword is one of the strongest swords in the game and is popular among players. It has outstanding combo potential and allows players to move rapidly between attacks. It is a one-handed sword preferred mainly by players who enjoy a quick and nimble playstyle.

• Rengoku: This sword is a strong sword that comes in Legendary tiers and is considered to cause the second-highest damage in the game. It has good combo potential and two moves that require 150 and 350 mastery, respectively.

• True Triple Katana: This sword deals the highest damage per click and is one of the strongest weapons to use in PvP. It is a Mythical sword that can conquer just about anything, but it is not beginner-friendly.

Overall, Saber V2 is a good choice for players who are just entering Second Sea, while Shisui and Rengoku are good choices for players who prefer a quick and nimble playstyle and high damage output. True Triple Katana is a powerful sword but is not recommended for beginners.