There are 30 Alter Egos in total to find in Monark, they take the form of small dark red crystals that float in the air and are left behind by students with particularly strong senses of self. You will be able to see which Alter Egos you need to acquire by going to the 'Profiles' menu on your cell phone. The characters that have a diamond shape icon next to their name have an Alter Ego you have not yet found and interacted with. If you read their bio you will be able to get hints as to where their location is. Once found the diamond shape will turn from a blank gray icon into a crystal icon. This Alter Ego Locations guide will tell you where to find them all.
Perrine Ikejuri
Location: First Year Building, First Floor, Art Room
Stat Increase: PSY +3
Koichi Izumi
Location: Club Block C, Second Floor, Track and Field Room
Stat Increase: ATK +5
Reiko Izumi
Location: Memorial Garden
Stat Increase: DEF +3
Hikari Kioi
Location: Library, Second Floor, West Wing
Stat Increase: AGI +6
Kanade Kitagawa
Location: First Year Building, First Floor, Classroom 1-A
Stat Increase: HP +8
Chris Carpenter
Location: Club Block A, First Floor, Corridor
Stat Increase: LUK +3
Miho Sonobe
Location: First Year Building, Third Floor, Classroom 1-F
Stat Increase: HP +6
Hidefumi Yoshida
Location: First Year Building, Rooftop
Stat Increase: HP +6
Kenyu Umezawa
Location: Second Year Building, First Floor, Classroom 2-B
Stat Increase: ATK +3
Mitsuyasu Jinbo
Location: East Street
Stat Increase: DEF +4
Takamori Suzuki
Location: Entrance Street
Stat Increase: AGI +5
Miyu Tachibana
Location: Main Building, Second Floor, Corridor
Stat Increase: ATK +6
Anna Hatta
Location: Club Block C, First Floor, Corridor
Stat Increase: LUK +5
Akira Brown
Location: Library, First Floor
Stat Increase: LUK +2
Rinne Asahina
Location: Main Building, First Floor, Corridor
Stat Increase: PSY +3
Yushuo Okawa
Location: Club Block C, First Floor, Corridor
Stat Increase: AGI +3
Mirai Otomo
Location: Central Street
Stat Increase: PSY +4
Junichiro Shigeno
Location: Second Year Building, Second Bloor, Biology Lab
Stat Increase: AGI +3
Mihono Takagi
Location: West Street
Stat Increase: DEF +4
Jo Nijima
Location: Main Building, Second Floor, Classroom 3-A
Stat Increase: ATK +2
Yunichiro Shigeno
Location: Club Block C, First Floor, Baseball Club
Stat Increase: HP +3
Hina Maisaka
Location: Archives, Second Floor, Special Exhibition Room
Stat Increase: PSY +5
Yoshika Machimura
Location: Main Building, Second Floor, Classroom 3-D
Stat Increase: ATK +4
Tetsuya Mihara
Location: Club Block C, First Floor, Storage Closet
Stat Increase: HP +8
Shigeyuki Mura
Location: Old Dormitory, Courtyard
Stat Increase: DEF +6
Shiro Sato
Location: Main Building, Rooftop
Stat Increase: PSY +5
Hiroki Suzuya
Location: Second Year Building, First Floor, Staff Room
Stat Increase: HP +5
Teruhide Takahashi
Location: First Year Building, First Floor, Staff Room
Stat Increase: HP +4
Risa Hayashibara
Location: Main Building, Third Floor, Music Room
Stat Increase: DEF +3
You will be able to find the last Alter Ego in the third tab of the 'Profiles' menu. It is in the same list as Vanitas and the character that has it is Mitsuru Hasegawa. In order to bring her into the game you must wish for her to rebirth which is done by defeating each of the Monarks again using special sign numbers, and then defeat the final boss for a second time. Once you have accomplished this you can wish Mitsuru Hasegawa revived and talk to her. The last Alter Ego can then be found in the infirmary, it will provide a stat increase of AGI +4.
Take a look at our Beginner Tips and Tricks to get help in Monark.