How appropriate is one column table

Does this kind of design come along with overhead or data redundancy? The structure of tables should remain able to do CRUD on tag, for something like manga/anime tag, allowing specific resources found-able through selection of tags. * representing primary key.

tag     (tagID*, tagName)
tagMap  (tagSetID*, tagID*)
tagSet  (tagSetID*)
announce    (announceID*, tagSetID, title, content)

Answer

There is nothing at all wrong with your design. Most of the time, we might expect the tagSet table to also maybe have a name column, e.g.

tagSet (tagSetID*, tagSetName)

That you don’t have one isn’t really an issue. This is really a standard many to many relationship between tags and sets, with the tagMap table serving as the junction table.