qemu-ga, the qemu guest agent daemon (https://www.qemu.org/docs/master/interop/qemu-ga.html), is a program that runs in the guest voluntarily let the host coordinate things with it like time changes.
The emulators/qemu package is mainly useful on the host, pulls in a large collection of dependencies like the graphics stack for drawing graphical output from the guest, and weighs over half a gigabyte.
What the guest needs is much more modest and shouldn't need to pull in any of these dependencies, so it should be available in a separate and much smaller package, say sysutils/qemu-guest-agent or sysutils/qemu-ga.