The Ospreys star started at openside flanker in his first test match as Wales beat Eddie Jones’ Japan 22-18 in Osaka.
The squad travel to Tokyo on Sunday ahead of the second test and King was pleased to mark his first cap with a victory.
“Obviously I’m delighted to get my first cap under the belt,” said King.
“It was as tough as we imagined out there.
“Throughout this trip we haven’t under estimated how good Japan are and you could see that from the display today.
“In the first half they brought the game to us and as I said earlier in the week we had to try and cope with the pace they play the game at.
“At half-time we talked about what was happening and what was going wrong and we changed the game plan a little and we implemented that and won the game because of it.”
The 22-year-old, played 24 time for the Ospreys this season and is looking for more test game time.
“I really enjoyed it and hopefully there will be plenty more to come,” he added.
“I hope I played well, we will have to look back at the video but I was delighted to be out there and getting the win for Wales.”
