Since there is no official Visual Novel titled "Majikoi A4", you are most likely referring to Maji de Watashi ni Koi Shinasai! A-4, the fourth fandisc in the Majikoi series.
Maji de Watashi ni Koishinasai! A-4 (Majikoi A-4) is the fourth fan disc in the Majikoi A series. Unlike the main games, it focuses on specific side-character routes and "After Stories" for established heroines. Route Overview majikoi a4 guide
For more information and walkthroughs, check out the following resources: Since there is no official Visual Novel titled
This is the most important part. You cannot just start the game and play the true finale. majikoi a4 guide