Then I will put all the girls that will be in the harem of the protagonist, it is not a definitive list, so it will surely be included more_

1 - Celeste Joy (OC).

2 - Roxanne (Hoenn Gym Leader)

3 - Verity (From the Pokémon Movie: I choose you!)

4 - Nancy (Female protagonist of Pokémon White and Black 2)

5 - Leaf (From Pokémon Leaf Green and Fire Red)

6 - Koharu (From Pokémon Journeys)

7 - Liko (From the new Anime of Pokémon but with an alternative story made by me)

8 - Iono (Palde Gym Leader)

9 - May (We know her perfectly)

10 - Dawn (We already know her)

11 - Serena (Obviously)

12 - Shauna (From Pokémon X and Y)

13 - Lillie (From Alola Region)

14 - Mallow (From Alola Region)

15 - Lana (From Alola Region)

16 - Cynthia (Ehem)

17 - Marnie (From Galar Region)

18 - Gloria (Female Protagonist of Pokemon Sword and Shield)

19 - Liza (Female Protagonist from Pokémon Black and White)

20 - Bianca (From the fifth Pokémon Movie)

21 - Sonia (From Galar Region)

22 - Erika (Kanto Gym Leader)

23 - Lusamine (Lillie's mother)

24 - Jasmine (Jotho Gym Leader)

25 - Whitney (Jotho Gym Leader)

26 - Lisia (Pokémon Idol)

27 - Acerola (From Alola Region)

28 - Korrina (Kalos Gym Leader)

29 - Liza (Hoenn Gym Leader)

30 - Nessa (Galar Gym Leader)

31 - Cheryl (From Sinnoh Region)

32 - Lyra (Female protagonist of Pokémon Heart Gold and Soul Silver)

33 - Crystal (Female protagonist of Pokémon Crystal)

34 - Suggest me more if you want a specific girl :)

*Note: The girls aren't in order.

Little sisters: 

1 - Molly (From the third Pokémon Movie)

2 - Secret for the moment.