Name the sponge which is used as marriage gift and symbol of union till death.

Explanation

**Step-by-Step Solution:**

1. **Identify the Context**: The question asks for the name of a sponge that is used as a marriage gift and symbolizes union until death.

2. **Geographical Relevance**: Recognize that this sponge is specifically mentioned in the context of Japan, where it is traditionally gifted during marriages.

3. **Understanding the Symbolism**: The sponge is given as a bouquet after it has died, representing the idea of a couple being united until death.

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