This is one of the eight endings that the game has. There are a few things to note about this one, though:
Point #1: This is available to you should you be on a 3 heart or 2:1 heart path. If you have given Finnel all three points, then there's not much else to worry about, but make sure you still complete her Cosmosphere, just for the heck of it.
Point #2: In doing a 3 HP path, you cannot access Saki's Lv.8 CS to finish it anyway. In a 2:1 HP path, you must complete Finnel's Lv.8, as this will lock Saki's out and set you on the right path anyway.
As with any of the Phase 4 requirements, you must defeat MYU within 7 minutes and stop Saki from singing. After this, depending on either of the two points you've made sure of for Finnel's sake, just complete Phase 4 (all the way through fighting Ciela) and complete the game. This will play out after that.