How do you write sync ninja in Kanji?

There isn't a single perfect translation of "sync ninja" into Kanji, as it's a modern English phrase combining elements not directly represented in traditional Japanese vocabulary. The translation would depend heavily on the context and what aspect of "sync ninja" you want to emphasize.

Here are a few options, each with slightly different connotations:

* 同期忍者 (dōki ninja): This is the most literal translation, using 同期 (dōki) meaning "synchronization" or "simultaneous." However, it sounds somewhat awkward and might not convey the intended nuance of "ninja" as a skilled individual.

* 連携忍者 (renkei ninja): This uses 連携 (renkei) meaning "linkage" or "cooperation," implying a team working in sync. This might be a better choice if "sync" refers to teamwork.

* 瞬時忍者 (shunjitsu ninja): This uses 瞬時 (shunjitsu) meaning "instantaneous" or "momentary," suggesting a ninja acting with incredible speed and precision. This is good if "sync" refers to speed and timing.

* シンク忍者 (shinku ninja): This uses the katakana transliteration of "sync." This is straightforward but lacks the elegant feel of kanji.

Ultimately, the best translation depends on the specific context. If you can provide more information about how "sync ninja" is used, I can offer a more tailored translation.