
Hullo.
Radiant will never punish players for pursuing multiple girls, nor will certain relationships lock you out of others. Radiant is a harem game: players are in fact encouraged to go full throttle and romance every character without consequence. ← This is the best way to play this game. Just make smart choices and don't blatantly tell the game "hey I want this relationship to be over with x-girl" and you will be fine (the MC will work it out).
At most, the only consequences of these actions will be some mild drama or hurt feelings that players can fairly easily sort out via smart choices... but the end result will be the best/happiest possible outcome for all involved.
I hope that quells some of the concerns people were voicing here. Have fun.