All the choices needed to get every CG and ending. The good/bad endings are triggered by the final choice (aside from one of Ei’s).

Ei:

• Decide against it.

• Stay with them.

• Speak to Ei.

• Tell her the truth. (Alternatively, lying to her will lead to the the first bad end without reaching any route.)

• Go inside and inquire about the phone. (Alternatively, looking for another store will make it possible to reach another bad end.)

• Ask her parents / Ask her directly. (If you chose to look for another store previously asking her will lead to a bad end. Otherwise this choice doesn’t matter.)

• Walk off. (Calling Hana will lead to the alternate/bad ending.)

Hana:

• Accompany her.

• Go with Sachi

• Speak to Hana
  (The next two choices only affect dialogue, but they have no effect on the ending.)

• Blame her. (Blaming yourself leads to the bad end.)

Sachi:
Her route trigger is a branch off before just Toshi and Ei have the party. Going with Sachi during the outing with Ei and Hana makes her route accessible.

• Decide against it.

• Go with Sachi.

• Speak to Ei.

• Let her in. (Dismissing her will just lead back onto Ei’s route.)
  (Similarly, like Hana’s route the next choice doesn’t affect anything other than dialogue.)

• Take the drugs / Do not take the drugs.