As a Beta, stability is a major concern. Save scumming is almost required, not just for strategic reasons, but because the game is prone to crashing during specific event triggers. There are known memory leaks; playing for extended periods will slow the game to a crawl until the browser or application is refreshed.
Use items found or bought in the world to boost character EXP more quickly. For example, specific vegetables or sex shop items can be used for significant boosts. Key Locations & Character Spawns robozou 2 version 5.6 english beta 5