Throughout the game, you earn Affection Points with heroines through dialogue choices and by using Nozomu's squad to defeat "heart mark" enemies.

At the beginning of Chapter 10, you will enter a romantic relationship with whichever heroine has the most affection points. Ties are broken in the order Nozomi --> Satsuki --> Katima --> Naya --> Ruputna.

On the 2nd playthrough and afterwards, if you choose Narukana's dialogue choice in Chapter 8, the affection system is ignored and you will enter a romantic relationship with Narukana instead.

Choice 1
“Nozomi's lunch”: Nozomi +12 affection
“Satsuki's lunch”: Satsuki +10 affection

Choice 2
“Invite her over”: Nozomi +12 affection
“Don't worry about it”: Satsuki +10 affection

Mission: Recapture the Lands of Azuleir

Choice
“Go to the classroom”: Nozomi +12 affection
“Go to the cafeteria”: Satsuki +10 affection

Mission: March Through the Azule Plains

Mission: Search for the Prosia Record

Mission: Liberate Aigia
Defeat heart mark enemy using Nozomu's squad: +4 affection divided among heroines in squad

Choice
Go with Nozomi: Nozomi +12 affection
Go with Satsuki: Satsuki +10 affection
Go with Katima: Katima +20 affection

Mission

Mission: Seal the minions in the Deeplands
Defeat heart mark enemy using Nozomu's squad: +4 affection divided among heroines in squad

Mission: Defend the Tower
Defeat heart mark enemy using Nozomu's squad: +4 affection divided among heroines in squad

Mission

Choice 1
Chase after Senpai and Luputna: Satsuki +10 affection, Ruputna +30 affection
Call out to Katima and Naya: Katima +20 affection, Naya +30 affection

Choice 2
Lend Satsuki-senpai a hand: Satsuki +10 affection
Look for Katima: Katima +20 affection, go to Choice 2a
Visit Naya and the others' cafe: Naya +30 affection, go to Choice 2a

Choice 2a
Nozomi's concert: Nozomi +12 affection
Look for Luputna: Ruputna +30 affection

Mission: Break through the Slums and reach the Town
Defeat heart mark enemy using Nozomu's squad: +4 affection divided among heroines in squad

Mission

Mission

Mission: Reach Zetsu for a final duel
Defeat heart mark enemy using Nozomu's squad: +4 affection divided among heroines in squad

Choice (2nd+ playthrough only)
Reach out your hand: Narukana route
Stare: nothing

Mission
Defeat heart mark enemy using Nozomu's squad: +10 affection divided among heroines in squad
9 squads total
Defeat special heart enemy using Nozomu's squad: +20 affection divided among heroines in squad

*Since Satsuki is not present, for this chapter only Talia acts as a "substitute Satsuki"; in other words defeating a heart enemy with a squad containing Nozomu and Talia earns affection for Satsuki.

Choice (during mission)
Senpai: Satsuki +10 affection
Nozomi: Nozomi +10 affection
Ruputna: Ruputna +10 affection
Katima: Katima +10 affection
Naya: Naya +10 affection