From Scratchpad

For this quest, Snakeman will send you to the Jakyo Manor Master. The Master needs ten Soul Shards(魂のかけら), an item that is dropped by Kodamas(コダマ). However, the Kodamas on the field have a very low drop rate for this story item, which is why the Master hands you a bronze plate and sends you to the Suginami Dungeon.

The Sugimani Dungeon is marked on the Suginami map by a large 'D' symbol, so head there. At this dungeon, the kodamas will have a much higher rate of dropping Soul Shards, so gather them here. However, Kodamas do not appear that often in the dungeon, so you may have to run the dungeon twice(or more) before you can get all ten shards.
Once you gathered the shards, return to the Master.

Once you finished your conversation with him, report back to Snakeman. He will read the Master's report, and then hand you a one thousand five hundred makka reward.

NOTE: You do not need to actually go through the dungeon. You can just buy the Soul Shards from other players and still be able to complete the quest.