AFAICT the Bella scene cleaning up the MC's new room is governed by three prior decisions.
If the MC did not visit Bella in the library in Episode 3 (and subsequently make out with her), Bella will not call the MC at all.
If the MC did visit Bella in Episode 3, Bella will call the MC offering to help clean his room. What happens next depends on whether or not the MC has had any lewd scenes with Bella.
If the MC got Bella's lewd scene in Episode 4 which requires staying with her during the episode), or her lewd scene in Episode 5, the MC will automatically accept Bella's offer (and even turn down Maya & Josy's offer if he is on their path). This will automatically lead to a lewd scene with her once the cleaning is done.
If the MC visited Bella in the library in Episode 3 but did not make any move on her in Episodes 4 or 5, the MC will have the option to accept or reject Bella's offer of help. If he accepts, it plays out as above. If he rejects, there is no lewd scene with Bella. The MC will note that he did not want to lead her on and is no longer pursuing a relationship with her.
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