Using his Soap Bubble Ninjutsu, Utakata creates acidic bubbles. Due to the nature of the bubbles they can be targeted at a specific spot or used as a wide-spread attack. These bubbles burn the opponent when popped.
Santōka is the given name of Santōka Taneda (種田山頭火, Taneda Santōka). He was a haiku poet, well-known for his free style haiku lacking the traditional 5-7-5 syllabic rule and seasonal word. He is called a wandering poet for the many trips he took in his later life as a Buddhist monk, wandering through Japan without being part of a monastery.
The san in Santōka's name is actually written with the kanji for mountain (山), but for this technique, it is interpreted as acid (酸), also pronounced san. Tōka is interpreted as meaning permeation (透過) instead of head (頭) and fire (火), which it means in Santōka's name.
Though not seen in the manga, the databook states that Utakata was capable of combining acid with his Soap Bubble Ninjutsu.