[pkg-gnupg-maint] Debian 9 brought unwanted process to my home!

[!?]

Hey, I've upgraded to Debian 9 from 8, and I found that GPG is
creating many lines in my log.

systemd[x]: Listening on GnuPG cryptographic agent and passphrase cache (restricted).
systemd[x]: Reached target Timers.
systemd[x]: Listening on GnuPG network certificate management daemon.
systemd[x]: Listening on GnuPG cryptographic agent (ssh-agent emulation).
systemd[x]: Listening on GnuPG cryptographic agent (access for web browsers).
systemd[x]: Listening on GnuPG cryptographic agent and passphrase cache.

How can I kill|disable gpg-agent? I don't want this.
Also, can I just apt-get remove this thing? I don't use GPG in this box.
(I saw someone wrote GPG broke APT, so I'm not sure about removing.)

--
I like GPG. I'm using it to encrypt emails on other PC.
But I hate GPG's gpg-agent. It's a waste of resource. I always kill that process
after encryption/decryption.

So.

How can I kill|disable gpg-agent?