Fick, who joins Edinburgh Rugby’s academy this summer, comes into the number 9 jersey in place of Asa Stewart Harris, who drops to the bench.
The highly-rated scrum-half – who qualifies for Scotland through his grandfather from Inverness – will partner Jake Dalziel at half-back.
Dan Kelly continues to lead the way out wide, keeping his spot on the wing after scoring in both of Scotland’s opening two matches.
In the pack, Christian Lindsay switches from the back row into the second-row, while Sam Byrd comes into the back row as Alfie Blackett drops out of the squad.
They’re joined in the matchday 23 by Rory McHaffie, Henry Kesterton, Nairn Moncrieff, Ollie Blyth-Lafferty, Jack Utterson and Jamie Stewart, giving Edinburgh Rugby a strong presence across the park.
Scotland go into the match in fine form, having seen off Italy before pushing New Zealand all the way, and face a Japan side who have lost their opening two games of the tournament.
Head coach Fergus Pringle said: “Last Thursday was a brilliant test for the group against New Zealand and there were areas of the performance that we took a lot of heart from.
“The never-say-die attitude from the team in that game was something I was very proud of. To score in the final moments showed that this group of players never give up and, coupled with the win over Italy, we go into Tuesday’s match with a lot of confidence but also a desire to right some of the things that could have gone better against New Zealand.
He continued: “We have full respect for the Japanese who we know will give us a stern test.
“We’ve made a few tweaks to the team which we thought was important given this is the third game in quick succession, but consistency in a number of areas was key too as we want to continue the good work done in the first couple of games.”
Scotland U20 team to play Japan in the 2026 World Rugby Junior Championship at the AIA Arena, Kutaisi, Georgia
Tuesday 7 July (kick-off 3.30pm local time, 12.30pm BST) – live on Premier Sports and Rugby Pass TV:
15. Rory McHaffie (Edinburgh Rugby)
14. Daniel Kelly (Edinburgh Rugby)
13. Campbell Waugh (Glasgow Hawks)
12. Henry Kesterton (Edinburgh Rugby)
11. Nairn Moncrieff (Edinburgh Rugby)
10. Jake Dalziel (Merchiston Castle/Newcastle Red Bulls
9. Matthew Fick (Edinburgh Rugby)
1. Ollie McKenna (Glasgow Warriors)
2. Joe Roberts (Glasgow Warriors) CAPTAIN
3. Ollie Blyth-Lafferty (Edinburgh Rugby)
4. Christian Lindsay (Edinburgh Rugby)
5. Dan Halkon (Glasgow Warriors)
6. Sam Byrd (Edinburgh Rugby)
7. Jack Utterson (Edinburgh Rugby)
8. Harvey Preston (Glasgow Hawks)
Replacements
16. Jamie Stewart (Edinburgh Rugby)
17. Jamie McAughtrie (Ayr RFC)
18. Jackson Rennie (Glasgow Warriors)
19. Finlay Mather (Grammar Tec)
20. Oliver Finlayson-Russell (University of St Andrews)
21. Asa Stewart Harris (Saracens)
22. Alex Bryden (Glasgow Warriors)
23. Ewan Caven (Gloucester Rugby/Nottingham University)