The Japanese Katakana symbol for Tsu.
Not to be confused with the Katakana for Shi, which has the rightmost stroke at a more gradual angle and the left strokes at a slightly more gradual angle as well. Another clue, the rightmost stroke on both symbols will often have a wider end where the stroke began. On Tsu this would be on the upper-right side, and the lower left side on Shi.