user1398: status-completed
This bug applies to any page with a tag editor (ask question, edit question, edit tags, etc.). The synonym tags do not show up in the list of available tags when the name is partially typed.
Using assassination-classroom as an example, it currently has ansatsu-kyoushitsu as synonym. However, ansatsu-kyoushitsu doesn't show up when ans is typed in the tag editor.
This totally defeats the purpose of having Japanese tag synonyms, as they are supposed to help user to find the correct series tag.

status-completed
The desired behavior is the current behavior in the search box of tags listing. It turned out that it is also buggy.
While the search box works with ansatsu-kyoushitsu, it doesn't work with the-legend-of-koizumi when searching for koi (it is a synonym of mudazumo-naki-kaikaku).

user1499: Wow, good find.  
This is a four-year-old bug that affected master (i.e. target of synonym) tags containing hyphens.
A fix will be pushed out shortly.

1398: <p><a href="/questions/tagged/status-completed" class="post-tag moderator-tag" title="show questions tagged &#39;status-completed&#39;" rel="tag">status-completed</a></p>

<p>This bug applies to any page with a tag editor (ask question, edit question, edit tags, etc.). The synonym tags do not show up in the list of available tags when the name is partially typed.</p>

<p>Using <a href="https://anime.stackexchange.com/questions/tagged/assassination-classroom" class="post-tag" title="show questions tagged &#39;assassination-classroom&#39;" rel="tag">assassination-classroom</a> as an example, it currently has <a href="https://anime.stackexchange.com/questions/tagged/ansatsu-kyoushitsu" class="post-tag" title="show questions tagged &#39;ansatsu-kyoushitsu&#39;" rel="tag">ansatsu-kyoushitsu</a> as synonym. However, <a href="https://anime.stackexchange.com/questions/tagged/ansatsu-kyoushitsu" class="post-tag" title="show questions tagged &#39;ansatsu-kyoushitsu&#39;" rel="tag">ansatsu-kyoushitsu</a> doesn't show up when <code>ans</code> is typed in the tag editor.</p>

<p>This totally defeats the purpose of having Japanese tag synonyms, as they are supposed to help user to find the correct series tag.</p>

<hr>

<p><a href="/questions/tagged/status-completed" class="post-tag moderator-tag" title="show questions tagged &#39;status-completed&#39;" rel="tag">status-completed</a></p>

<p><s>The desired behavior is the current behavior in the search box of <a href="https://anime.stackexchange.com/tags">tags listing</a>.</s> It turned out that it is also buggy.</p>

<p>While the search box works with <a href="https://anime.stackexchange.com/questions/tagged/ansatsu-kyoushitsu" class="post-tag" title="show questions tagged &#39;ansatsu-kyoushitsu&#39;" rel="tag">ansatsu-kyoushitsu</a>, it doesn't work with <a href="https://anime.stackexchange.com/questions/tagged/the-legend-of-koizumi" class="post-tag" title="show questions tagged &#39;the-legend-of-koizumi&#39;" rel="tag">the-legend-of-koizumi</a> when searching for <code>koi</code> (it is a synonym of <a href="https://anime.stackexchange.com/questions/tagged/mudazumo-naki-kaikaku" class="post-tag" title="show questions tagged &#39;mudazumo-naki-kaikaku&#39;" rel="tag">mudazumo-naki-kaikaku</a>).</p>
 1499: <p>Wow, good find.  </p>

<p>This is a four-year-old bug that affected master (i.e. target of synonym) tags containing hyphens.</p>

<p>A fix will be pushed out shortly.</p>
