Yasuko is from the Japanese yasu (安 — peace, calm) + ko (子 — child) — peaceful child. Yasuko Takasu is a character in Yuyuko Takemiya's Toradora! series finale became a emotional plot driver.
Yasuko does not currently appear in the US Social Security Administration's top 1,000 girls' names, so we don't publish a US rank or birth count for it. That says nothing about the name's standing elsewhere in the world — only that it sits outside the ranked US data we rely on.
—
In Pythagorean numerology the letters of Yasuko reduce to 2, The Peacemaker. This is a traditional interpretive system, not a factual claim about the name.