If you receive the message "You see nothing out of the ordinary," simply wait for the leeches' bodies to vanish. Then you can get the coral by checking the ???. Not everyone has this issue.
If more than one party member needs this fight, only one person needs to pop the three leeches. After the last leech fades away, have a different party member who needs the item click the ???, then have the player who spawned the leeches click it afterwards. Otherwise the player who did not spawn the leeches will be unable to obtain the Strangely Shaped Coral.
Return the dagger to Ensetsu for a cutscene that finishes the quest.
Notes
The Korroloka Leeches immediately attack the player who examines the ???. If this player is low-leveled, he may die from this. It is a good idea to have that player use Sneak (item/spell/ability) to prevent this, or have another player use an AoE attack to quickly attract the leeches' attention.
It is not necessary to kill all three leeches. If you hold one leech without aggroing or linking the other two, you can wait for the two passive leeches to despawn. Then, you can kill the leech you were holding and receive credit for the fight. The game only checks that the last remaining leech is defeated. Note that spawning the leeches and letting all three despawn does not allow you to get the key item.
Kaede: Hey, Have you heard of my sister Ayame? She's a samurai and a member of the Mythril Musketeers. She's so cool. Me? I'm nothing compared to her...
Kaede: But I was thinking. If I could use a katana, too, I could be cool and strong like her.
Kaede: But when I asked my dad about it, he got mad and said I couldn't.
Kaede: My dad's been acting strange lately. I think that he's been visiting that Kagetora from the Tenshodo.
Ensetsu: Kaede? What are you up to now? You know you shouldn't be bothering our visitors.
Kaede: I hate you! Why won't you tell me the truth!?
Ensetsu: I'm sorry that you had to see that... Girls these days grow up so fast. What is a father to do?
Ensetsu: One day, I know I'll have to tell her the truth about...
Ensetsu: Excuse me. I know you must be busy, but could I ask a favor of you?
Ensetsu: I would like to buy something back that I recently sold through the Tenshodo. However, I was told by Kagetora that it was already been shipped to Norg.
Ensetsu: He told me that if I bring him some strangely shaped coral from the Korroloka Tunnel, he would return my item.
Ensetsu: However, there is no way I would survive a trip to that tunnel... I would be in your debt if you could travel there in my place.
This article is missing a video of the battle, mission, or quest. You can help by adding it.
Ensetsu: I hate to ask you again after all the trouble you have gone through, but would it be too much to ask you to take that strangely shaped coral to Ryoma in Norg? I would be in your debt...
This article is missing a video of the battle, mission, or quest. You can help by adding it.
Ensetsu: I cannot express in words the gratitude I feel towards your kindness. I sold this to help support my family, but then I realized that my daughter needed it one more.
Kaede: What is that? You bought another sword for Ayame, didn't you? It's just not fair!
Ensetsu: Would you stop going on about that! I have never purchased a weapon for your sister. Every katana she owns was acquired without my, or anyone else's, help.
Ensetsu: Long ago, Yomi...your mother and I lived in Norg. Norg is a haven for the arts of the Far East.
Ensetsu: I was just a lowly crew member on a pirate ship. Your mother, on the other hand, was a master of ninjutsu--almost as strong as she was beautiful...
Ensetsu: And that's probably why she found comfort in a normal, boring man like me.
Ensetsu: When we found that your mother was carrying your sister, we left Norg and traveled here in search of a more simple life.
Ensetsu: It was at the time that your mother told me this: she was proud of the road she taken, and it was that very road that led her to her new life.
Ensetsu: The hardships that she led to endure made her into the strong mother that she was.
Ensetsu: Perhaps at that time, she realized that she did not have much longer in this world...
Ensetsu: But she fought for ten long years until she exchanged her life for the life of our second daughter...you, Kaede.
Ensetsu: I never wanted you or your sister to take up the katana.
Ensetsu: When your sister said she wanted to travel to Norg to study the way of the samurai, of course I was against it. However, if it was to keep her from becoming a ninja...
Ensetsu: Kaede... Each day, you remind me more and more of your mother.
Ensetsu: And that's why I have been so prtective of you. But maybe I was wrong...
Ensetsu: Unlike most fighters, ninjas do not just wave their swords. They lurk in the shadows and stalk their enemies. One must have the highest level of patience and concentration to draw that blade.
Ensetsu: Your mother left this blade sheathed to remind her of that, and now this blade will be passed on to you.
Ensetsu: The road you travel is for you to decide, but do not forget the message that remins in your mother's katana.
Ensetsu: I thank you so much for your help in bringing the blade back to my home. I do not have much to offer you, but take this scroll detailing the secrets of the ninja as a token of my appreciation. It was my wife's.
Ensetsu: No, Kaede won't be needing it. All she really needed was her mother's strong will and spirit. If she wishes to walk the path Yomi chose, it will be her decision.
Ensetsu: But i have the feeling she will be traveling to Norg soon...to find that path.