A Distant Road (はるかな道, Harukana Michi) is the last stage in Silver Week.
At the start of the battle, 1 Metal Hippoe will appear. After 20 seconds, 2 more will spawn, and 3 more spawn after ~66 seconds. When the enemy base is hit and goes down to 99% HP, it'll spawn 1 Golden R. Ost and 3 each of Metal Hippoe and Steel Snake. After defeating 1 or 2 enemies, Mercury Sloth will appear with Super Metal Hippoe and some more Steel Snakes. The 2nd Golden R. Ost will appear 40 seconds after the first one.
This stage can be beaten easily with Catornado or units with guaranteed Critical Hits. If you don't have either, Moneko, Space Cat, Jurassic Cat and Lion Cat are still enough to beat the stage, but it could take many attempts.
The main problem encountered while playing the stage is the stack of Metal Enemies. You'll need fast area attackers to dispatch those Metal Hippoes and Steel Snake, and ranged Critical Hitters to land hits on Golden R. Ost, Mercury Sloth and Super Metal Hippoe.