Kindly refer to this video for your reference.
*Thanks to PowerPyx for the video.
Below shows all the spring location that must bathed in order to get the trophy.
Mission name (Region)
1 - Deep in the Shadows (Kyushu)
2 - The Spirit Stone Slumbers (Kyushu)
3 - The Silver Mine Writhes (Chugoku)
4 - The Ocean Roars Again (Chugoku)
5 - Spider Nest Castle (Kinki)
6 - Falling Snow (Kinki)
7 - The Demon of Mount Hiei (Kinki)
8 - The Iga Escape (Tokai)
9 - Memories of Death-Lilies (Tokai)
10 - The Trail of the Master (Tokai)
11 - The Trail of the Master (Tokai)
12 - The Trail of the Master (Tokai)
13 - The Trail of the Master (Tokai)
14 - The Trail of the Master (Tokai)
15 - The Trail of the Master (Tokai)
16 - The Trail of the Master (Tokai)
17 - Immortal Flame (Sekigahara)
18 - A Defiled Holy Mountain (Omi)
19 - The Samurai from Sawayama (Omi)
20 - The Demon King Revealed (Omi)
*Thanks to rubhen925 for the last location