The option to play in windowed mode is now available.
To access the previous build to keep your saves: go to your Steam library -> right click Hoshizora no Memoria -Eternal Heart- HD -> properties -> betas -> select launch branch -> wait for the update and start playing.
If the option for the launch branch isn't appearing please restart your Steam client. The windowed mode version will not be compatible with your previous saves so please keep this in mind when swapping over. Trying to access previous saves will result in a crash. It is not possible to resize the window when playing either. This is exactly the same as the original Japanese HD release. Please let us know if you encounter any issues when playing. We hope you enjoy Hoshizora no Memoria -Eternal Heart- HD.