Amagami Wiki

The prerequisite for unlocking Risa Kamizaki is to have seen the bad end or the close friend end with each of the other six main heroines.

In order to get the best end for Risa, you will also need to be at level 3 love with at least one other heroine. Haruka Morishima is probably the easiest to obtain this status with, so plan accordingly.

After the Second conversation period on Day 5, a compulsory event will occur - this is an indication that the flags have been met and the choices here won't impact the ending.

After school on the 38th day, a compulsory event will occur. Any choice you make here is fine.

On day 40, make a save during the second day period because there will be a compulsory event during the third period.

During the conversation that follows:

  1. Option 1
  2. Any option
  3. Option 3 for best end, option 2 to end the route but progress Miya's route

Talking with Risa Kamizaki

During the lunch period, select the conversation option for Risa that will appear on the map. During the conversation that follows(02,33), select the following topics (choices are the same for Ebikore+ and original):

  1. Gossip, studying, food, or love
  2. Gossip, entertainment, food, or ecchi
  3. studying, entertainment, love, or ecchi
  4. exercise, fashion, love, or ecchi
  5. Attack

During the Christmas Eve event, choose the conversation option that goes like "I want you to tell me your reasons. I want to resolve this together". If you instead select the other option, it will lead to the bad end. You can choose any answer to the question that follows.

Ebikore+ Players: There is a "deepen your trust" event for every heroine other than Ayatsuji which will make it impossible to progress with Kamizaki's route. Avoid these routes if you are going for Risa. These events are: Rihoko (32,13), Kaoru (55,21), Sae (07,21), Nanasaki (11, 44), and Morishima (50,35).

Information is from this wonderful Japanese Amagami guide