The goal of the game is to survive by shooting zombies before they touch the red line. If a single zombie makes it through the game ends. Resident Evil: Zombie Busters has bosses too. Yes, the Tyrant is in the game. After you take him down you can compare your score with others via the online leaderboards.
Resident Evil: Zombie Busters is only available for Japanese cell phones. Visit Famitsu for more screenshots of Capcom’s zombie shooter.