For starters, the Baseball route is the event following up the laser tag route. This route, despite being not a "happy end Light orb" one, it is still fun. To access it, you only need to "avoid" fulfilling all flags of any character of school life routes.
However, to access Baseball route, additional conditions are required along with those for the laser tag:
- Nagisa: Meet her in the courtyard / be concerned. From here, you can ignore her. However, if you buy her a bread in a hurry, you must not help for the drama club.
- Tomoyo: See what happens / interested / go and see / follow Sunohara *3 / helps her. Afterwards, you can ignore her. be sure to NOT take all her flags, otherwise you might end in her route. The safest way is to come late at school the 21st april.
In any case, Tomoya must be close enough with Tomoyo so she will take part of the laser tag. If she isn't present, it is a game over.
- Laser tag route: you must be able to defy akio and pull a draw. If you are defeated by either Tomoyo, Kyou or Akio, you won't be able to get to the baseball route.
Winning conditions:
VS Tomoyo: choose "give her advice"
VS Kyou: choose "I feel sorry for her, so I will stop Sunohara"
VS Akio: choose "Let sunohara buy food"
If everything goes well, Akio and Tomoya will end on a draw. Instead of going to a bad end, the route will continue and Akio will bump on Tomoya, the former asking help for a baseball match.
Now, from there, there are 3 possible outcome:
The outcome depends of the characters in your team.
If you are short of 3 members, the 3 bench members will be added, which will lead to the first outcome.
If you are short of 1 or 2 members (so recruiting only 1 among the 3), Sanae (and then Ryou if you are short of 2) will help, but you will get the second result.
If you are able to get full house right from the bat (so the 3 recruitable characters), the third outcome will happen.
To recruit these characters, there are some conditions:
Here is a "perfect" walkthrough for your convenience. I used the terms used with the unofficial english translation patch.