Hello.
I was able to get the log, so I will describe it below.
Oct 29 22:02:50 sv01 systemd[1]: Started Caddy.
Oct 29 22:02:50 sv01 caddy[21215]: caddy.HomeDir=/var/lib/caddy
Oct 29 22:02:50 sv01 caddy[21215]: caddy.AppDataDir=/var/lib/caddy/.local/share/caddy
Oct 29 22:02:50 sv01 caddy[21215]: caddy.AppConfigDir=/var/lib/caddy/.config/caddy
Oct 29 22:02:50 sv01 caddy[21215]: caddy.ConfigAutosavePath=/var/lib/caddy/.config/caddy/autosave.json
Oct 29 22:02:50 sv01 caddy[21215]: caddy.Version=v2.2.1
Oct 29 22:02:50 sv01 caddy[21215]: runtime.GOOS=linux
Oct 29 22:02:50 sv01 caddy[21215]: runtime.GOARCH=amd64
Oct 29 22:02:50 sv01 caddy[21215]: runtime.Compiler=gc
Oct 29 22:02:50 sv01 caddy[21215]: runtime.NumCPU=4
Oct 29 22:02:50 sv01 caddy[21215]: runtime.GOMAXPROCS=4
Oct 29 22:02:50 sv01 caddy[21215]: runtime.Version=go1.15.2
Oct 29 22:02:50 sv01 caddy[21215]: os.Getwd=/
Oct 29 22:02:50 sv01 caddy[21215]: LANG=ja_JP.UTF8
Oct 29 22:02:50 sv01 caddy[21215]: PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin
Oct 29 22:02:50 sv01 caddy[21215]: HOME=/var/lib/caddy
Oct 29 22:02:50 sv01 caddy[21215]: LOGNAME=caddy
Oct 29 22:02:50 sv01 caddy[21215]: USER=caddy
Oct 29 22:02:50 sv01 caddy[21215]: INVOCATION_ID=473da4015af44ad2b1003f61616e5912
Oct 29 22:02:50 sv01 caddy[21215]: JOURNAL_STREAM=9:340637
Oct 29 22:02:50 sv01 caddy[21215]: {"level":"info","ts":1603976570.760716,"msg":"using provided configuration","config_file":"/etc/caddy/Caddyfile","config_adapter":""}
Oct 29 22:02:50 sv01 caddy[21215]: {"level":"info","ts":1603976570.7630746,"logger":"admin","msg":"admin endpoint started","address":"tcp/localhost:2019","enforce_origin":false,"origins":["localhost:2019","[::1]:2019","127.0.0.1:2019"]}
Oct 29 22:02:50 sv01 caddy[21215]: {"level":"info","ts":1603976570.763887,"logger":"tls.cache.maintenance","msg":"started background certificate maintenance","cache":"0xc000277260"}
Oct 29 22:02:50 sv01 caddy[21215]: {"level":"info","ts":1603976570.765915,"logger":"http","msg":"enabling automatic HTTP->HTTPS redirects","server_name":"srv0"}
Oct 29 22:02:50 sv01 caddy[21215]: {"level":"info","ts":1603976570.7672238,"msg":"autosaved config","file":"/var/lib/caddy/.config/caddy/autosave.json"}
Oct 29 22:02:50 sv01 caddy[21215]: {"level":"info","ts":1603976570.767244,"msg":"serving initial configuration"}
Oct 29 22:02:50 sv01 caddy[21215]: {"level":"info","ts":1603976570.7679405,"logger":"tls","msg":"cleaned up storage units"}
Oct 29 22:02:57 sv01 caddy[21215]: {"level":"info","ts":1603976577.3398793,"logger":"http.log.access","msg":"handled request","request":{"remote_addr":"126.xxx.yyy.zzz:5516","proto":"HTTP/2.0","method":"GET","host":"riku22.me","uri":"/","headers":{"Te":["trailers"],"User-Agent":["Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:82.0) Gecko/20100101 Firefox/82.0"],"Accept":["text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8"],"Accept-Language":["ja"],"Accept-Encoding":["gzip, deflate, br"],"Upgrade-Insecure-Requests":["1"],"Pragma":["no-cache"],"Cache-Control":["no-cache"]},"tls":{"resumed":false,"version":772,"cipher_suite":4865,"proto":"h2","proto_mutual":true,"server_name":"riku22.me"}},"common_log":"126.xxx.yyy.zzz - - [29/Oct/2020:22:02:57 +0900] \"GET / HTTP/2.0\" 0 0","duration":0.000007163,"size":0,"status":0,"resp_headers":{"Server":["Caddy"]}}
Oct 29 22:02:57 sv01 caddy[21215]: {"level":"info","ts":1603976577.4921696,"logger":"http.log.access","msg":"handled request","request":{"remote_addr":"126.xxx.yyy.zzz:5516","proto":"HTTP/2.0","method":"GET","host":"riku22.me","uri":"/favicon.ico","headers":{"Pragma":["no-cache"],"Cache-Control":["no-cache"],"Te":["trailers"],"User-Agent":["Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:82.0) Gecko/20100101 Firefox/82.0"],"Accept":["image/webp,*/*"],"Accept-Language":["ja"],"Accept-Encoding":["gzip, deflate, br"],"Referer":["https://riku22.me/"]},"tls":{"resumed":false,"version":772,"cipher_suite":4865,"proto":"h2","proto_mutual":true,"server_name":"riku22.me"}},"common_log":"126.xxx.yyy.zzz - - [29/Oct/2020:22:02:57 +0900] \"GET /favicon.ico HTTP/2.0\" 0 0","duration":0.000007013,"size":0,"status":0,"resp_headers":{"Server":["Caddy"]}}