ASHFORD ACADEMY PATH
NOTE: In order to open up this path, you must have already beaten the game once. On your first time through, only the Geass path will be available, and it won't matter how many times you talk to Kallen (who on subsequent playthroughs will start you down the Black Knights path) or Suzaku (Britannian military path) or Milly (Ashford Academy path).
The Common Part
If you like Milly, it is ridiculously easy to get her endings on this path -- just talk to her whenever you have the opportunity, and you're pretty much guaranteed. That's why this guide is geared at getting you any other ending! The focus is really to get you onto the Ashford Academy path (as opposed to the Geass, Black Knights, or Britannia path) without being doomed to date Milly.
HOW THIS GUIDE WORKSThe Required Flags are options that you must take, but you do not have to take all of them where I've indicated. The flag where you talk to Milly in the church, for example, comes up several times. The only thing you need to be careful of is talking to Kallen or the shadow in the streets, because the Geass path and the Black Knights path are extremely easy to get onto. (Since the Britannian path takes longer to get started, it's safer to talk to Suzaku, so I did that several times.)
Since I wanted a Lelouch ending, I've avoided talking to any of the other girls except for where I absolutely had to. Wherever you see Lelouch, Suzaku, C.C., or Lloyd and Cecile, you can substitute in the female of your choice -- again, as long as it isn't Kallen, who you shouldn't talk to until you're firmly on the Ashford Academy path.
There will be a sequence of Student Council scenes. Choose X is you are not interested in Kallen; Triangle if you are.
Day 1Required Flag: Milly in the student council room. (Choose Circle, "Absolutely not," to lose points.)
* Lelouch. (Choose Triangle, "Sure thing," to gain points.)
* Suzaku. (Choose X to make him like you, Triangle to brush him off.)
Day 2Required Flag: Milly and Lelouch in clubhouse.
* Nunnally and Lelouch. (Choose Circle, "Maybe we are alike," to get points with both of them.)
* Nunnally and Sayoko.
Ambush: Milly. (Choose Square, "Not yet," to lose points.)
Day 3* Lelouch
* C.C. [Lelouch shows up.]
* Milly (the only other choice is Kallen, and talking to Kallen is risky)
Day 4* Lelouch
* Nunnally and Sayoko
* Milly (possibly an unnecessary visit, I was a little alarmed by my missing flags)
Day 5Required Flag: Milly in the church. (Choose Circle, "I don't think love is like you say," to lose points.)
* Suzaku and Nunnally
* Kallen and ? [Ougi]
Day 6* Nina (Square gains points, Triangle loses points, Circle is neutral)
* Required Flag: Kallen, Milly, and Shirley in the clubhouse. (Choose Triangle to question Milly, or choose Circle to side with Kallen or Square to side with Shirley.)
Day 7Required Flag: Milly in the clubhouse. (Choose Triangle, "I'm not so sure about that.")
Ambush: Entire Student Council.
Day 8Ambush: Entire Student Council.
* Lloyd & Cecile (since Lelouch, Suzaku, and Nunnally are all unavailable)
* Suzaku [vs. Nina or Milly] (Choose Square for likings, Triangle for less likings, and Circle for "IDK".)
* Lelouch (Choose Circle, "I'll wait a while." This or Square will get a CG of Lelouch playing chess; Triangle will end the conversation peremptorily.)
First Branching Decision!!
On your second time through the Ashford Academy Path, you will be given the opportunity to continue as normal or skip over to the Blue Moon path (PS2 version only). What will happen is that Rivalz will ambush you on the beginning of Day 8 and take you to Milly, who will eventually present you with a choice. Why are you here?
Triangle: "To go to school and (something something something)."
X: ".....I'd like to fall in love."
Triangle - Continuing the Ashford Academy Path
Day 8Ambush: Rivalz takes you to talk to Milly. (Choose Triangle.)
* Lloyd (to avoid everyone)
* Nina (to avoid everyone)
Day 9* Lloyd (to avoid everyone)
* Nina (to avoid Milly)
* Suzaku (no choice)
Second Branching Decision!! Do you want to actually end up with Milly and witness the engagement party sub-event? Then choose X when Milly ambushes you!
Triangle - No Engagement Party
Day 10* Lelouch in the clubhouse
Ambush: Milly. (Choose Triangle.)
* Rivalz (to avoid the girls, and also gain a CG of Rivalz on his motorcycle)
Event: Upon going to the library, you will learn some things about your mysterious past and have flashbacks. Go away, plot! We want to make Lelouch wear a dress.
Day 11* Lelouch
Event: Choose someone to go with you on an errand as you prepare for the school festival. (My options were Milly, Lelouch, Nina, and Rivalz. Naturally, with my goal, I chose Lelouch.)
* Rivalz and Nina (to avoid girls)
* Nina (to avoid Milly)
* Euphy (because why not!)
Day 12* Lelouch
Event: Choose another person. (This time: Milly, Suzaku, Shirley, Kallen. I chose Suzaku, of course.)
* Rivalz. Several CGs are netted this way, and you wind up with the option to geass Rivalz into forgetting that his first kiss was taken by SOME GUY and not Milly. :|||
* Nina (to avoid Milly and Euphy)
* C.C. (no choice), who talks to us about our geass use.
Day 13* Nunnally and Sayoko
Ambush: More errands! My choices this time are Lelouch, Nunnally, Suzaku, Nina. (Choose Lelouch.)
* Kallen, Nunnally, Shirley, and Rivalz. Another errands opportunity. (Choosing Nunnally.)
Day 14* Lelouch in the park.
Ambush: Errand time! Milly, Lelouch, Shirley, Kallen. (Choosing Lelouch.)
* Nunnally, except it's really on Sayoko.
* Lelouch, Nunnally, Suzaku, Nina. More errands! (Lelouch, of course.)
Day 15Ambush: Milly. (This is the engagement party choice, so what was that other one, sjdflksj. Well, Triangle says you understand, whereas X says you definitely won't forget.)
* Nunnally, Milly, Rivalz, Nina. (Choosing Nina.)
* Lelouch. (Choose Triangle to agree with him, X to disagree.)
* C.C., which nets a new CG.
Day 16* Suzaku (Triangle to wake him up, X to let him sleep.)
Ambushed: Entire Student Council.
* Suzaku, Kallen, Nina. (Choose X not to use your geass, just because using your geass a lot usually leads to bad endings. Either option causes Kallen to like you more, though.)
* Milly and Nina.
Day 17Event: The festival begins.
* Suzaku and Rivalz
Event: Cosplay Kiss. Whoever likes you the most will appear and wind up wearing an interesting outfit. Then you'll continue to a play with them, where Rai will recover more of his memories.
Finally, you wind up in a church and have a long discussion with the same person. (If you've spent too much time with Milly, she will appear here even if you didn't promise to remember the engagement party, but you'll still get an ending with whoever likes you second-best.)
After the church, terrorists will attack the school. After a scene and some more flashbacks, Rai will use his geass to end the threat by having all the terrorists kill themselves. Unfortunately, this horrifies all of your fellow classmates, and you'll have to geass them to forget what happened. (A brief bit of dialogue with C.C. features her emphasizing again that the "power of kings" is a power that isolates.)
Another batch of scenes will take place, and then you'll get your ending sequence! Doing exactly what I did, it should be a Lelouch ending.