This page explains whether you should save Kid or not in Chrono Cross: The Radical Dreamers Edition.
After sneaking into Viper Manor at night, Serge and company will narrowly escape capture. However, Kid will be inflicted with an elusive poison that probably cannot be cured.
At this point, you must make a hefty decision: whether to try and save Kid or not.
As it happens, regardless of what you choose, Kid will eventually survive. But because of your choice, the path you take will briefly diverge–and the characters you can recruit will differ.
If you Save Kid
This is the option most people will probably choose on their first playthrough. After all, it’s hard to leave someone to die, not knowing the possible consequences.
In this path, you’ll explore the Hydra Marshes in Home World to obtain the Hydra Humour required to save Kid. Pretty simple stuff, really.
The following characters can only be recruited if you choose to save Kid.
If You Don’t Save Kid
This is the option you pick if you’re a heartless scoundrel… Just kidding. Or you already know that Kid will survive regardless.
In this path, you’ll skip the Hydra Marshes and go straight to the Hermit’s Hideaway and S.S. Invincible sections.
The following characters can only be recruited if you choose to leave Kid behind.
Which Path to Choose?
There is no right or wrong answer. Choosing to save Kid is the more natural choice, so if in doubt, go with that. Otherwise, if you want to be efficient, choose not to save Kid, so you can recruit Glenn, who’s pretty dang amazing.
Besides, if you want to 100% this game, you’ll need to play through the game (or parts of it, at least) multiple times to recruit everyone. So there’s a good chance you’ll eventually end up going down the path you didn’t go earlier.