The stage is a canyon-like stage set near the sea that bares resemblance of Green Hill Zone via its checkerboard style cliff surfaces and grassy paths. Some of these paths also seem to engrave arrows which point the general direction the player should head towards to reach the goal.
As a tutorial level, Omochao will teach the player them the basic gameplay mechanics of Sonic Heroes, including each formation, their movesets and how they can be used to traverse sections and/or fight enemies throughout the level. The score is not recorded for this stage.
- The music that plays in this stage also plays in Seaside Hill of 2P Battle mode's Action Race and Seaside Course of Bobsled Race.
- As the player reaches the end of Sea Gate, the next stage, Seaside Hill, can be seen in the distance.
|"STAGE 00 : SEA GATE"||Jun Senoue||3:25|
|2P (E3 Demo)||Jun Senoue||3:25|