I posted a similar question regarding gradle but this question is without gradle or maven.
I can not get Kotlin working properly using Eclipse IDE. This works great
Add Kotlin Nature fixes the issue. Click on your project and Configure Kotlin -> Add Kotlin nature
This partially fixes the issue, though eclipse plugin is still buggy and auto import function still doesn't work for me.
If you're having any issue, make sure you have kotlin_bin folder added in your project. Also make sure that ALL kotlin files have the correct package name sometimes when you rename packages or move files around kotlin classes may not get updated.