This game has 2 endings. If you got both endings then you can jump to the next game in the series.
This game is not the first game to play. I think you are playing the games in the wrong order. The correct order to play the series is this one below:
3-A Happiness Story [Remastered]
7-Goodbye Time Traveler [Remastered]
8-CC : The Girl Who Chants Love At The Edge Of Time [Remastered]
9-Null
14-''End Of Happiness REMAKE''
17-Farewell My Happiness [Remastered]
18-Identity
19-Goodnight Mirall [Remastered]
20- Naz [Remastered]
21-Observer
22-SYSTEM
23-Hassan : A Happiness After Story
You can also find this play order in my profile here:
I made the following list for myself. What do you think about it? Does it worth it to play those extra versions?
1 (1) Happiness 1 REMAKE
2 (2) Happiness 2 [Remastered]
3 (3) A Happiness Story [Remastered]
4 (4) Existence (RPG)
5 (5) MILKER (RPG)
7 BUTTERFLY [Remastered] <2023>
8 (6) Butterfly [Remastered] <2024>
10 (7) Goodbye Time Traveler [Remastered]
11 CC: The Girl Who Chants Love at The Edge of Time
12 (8) CC: The Girl Who Chants Love At The Edge of Time [REMASTERED]
13 (9) Null: Anniversary Edition
15 Death Moon
16 (10) Devotion [Remastered]
17 (11) Time Letter [Remastered]
18 (12) Zero One [Remastered] <fouzi94>
19 ZERO ONE [Remastered] <strange-girl-studios>
20 Reeva
21 (13) Reeva [Remastered]
23 (14) End of Happiness [REMAKE]
24 (15) Divinity [Remastered]
25 (16) Carmine [Remastered]
26 (17) Farewell My Happiness [Remastered]
27 (18) Identity
28 (19) Goodnight Mirall [Remastered]
29 (20) Naz [Remastered]
30 (21) NULL 2 : Genesis (The Full Game)
31 (22) SYSTEM
32 (23) Observer
33 (24) Hassan : A Happiness After Story
34 (25) Waiting for Godot
35 Happiness Forever: The AI-Generated Game
P.S. You forgot about “NULL 2 : Genesis” in your comment.