School Shoes
From Inkipedia, the Splatoon wiki
The School Shoes are shoes in Splatoon. It is 2-star rarity obtained through the Inkling Girl amiibo.
Its ability is Ink Saver (Sub) which decreases amount of ink consumed by your Sub weapon.
Unlock
Complete these 4 missions the amiibo gives you to unlock it:
13 Shifting Splatforms — Midnight Rendezvous —
14 Octoling Assault — Skirmish at the Skatepark —
15 Undeniable Flying Object — Bluefin Sighting —
Boss 3 Roll with the Punches... The Rampaging Octowhirl!
Appearance
Abilities
The Power Boots come with the Ink Saver (Main) ability as a main ability.