Question about school club advisors

From what I understand, most (if not all) school clubs have a teacher acting as an advisor/sponsor. Is it plausible for some clubs to share an advisor?

Also, what do club advisors actually do? A lot of clubs in anime don't show the advisor, but anime doesn't always show reality.

From what I understand, most (if not all) school clubs have a teacher acting as an advisor/sponsor.

A teacher acts as an advisor but not as a sponsor. Club activities are available for school students about ten years old or older, and for those in high school and younger, there will always be an advisor. Otherwise, it's not an authorized school club activity. In some municipals, every teacher of a public school must even work as an advisor for at least one school club activity.

Is it plausible for some clubs to share an advisor?

It does happen, but teachers are already busy enough teaching their main subjects.

Also, what do club advisors actually do?

It really depends on the club and the teacher. But at least there is a limit to what high school students and those younger can do by themselves, because they are minors. They might need an adult to apply for an event or to book a work space. The advisor is supposed to help students do that. For many clubs, especially athletic clubs, the advisor even sometimes works as a coach. This happens more often when the advisor is particularly interested in the activity and actually has some extra skills than the students. In other cases, the advisor might help students find/hire a coach instead.

A lot of clubs in anime don't show the advisor, but anime doesn't always show reality.

The targeted viewers of anime about schools are usually students. So the student characters would be featured. They would be the heroes, and it would seem like everything is all done by themselves. In reality, however, especially in leading athletic clubs, not only the advisor but the parents of the club members play a big role.

Meanwhile, a lot of advisors may not be interested in the activities. Then you might not see the advisor at all. This does happen in real life, and in real life, when the students are not active enough the teachers lose interest, and then the students would become even less active because there would be no adult to lead them. Or if the students are so active and smart that they can achieve a lot of things all by themselves, the advisor has little to do.

Hope it helps.

Thank you very much!