Splitting the team takes more than counting units: Support the lower route and preserve enemy roadblocksMinor spoilers
Assess each route's threats. Send mobile units early if the lower route is understaffed, and check what lies behind a blocking enemy before defeating them.
Original video: “Mid-Autumn Festival means playing Fortune's Weave! Cai's route: September 25, 2026 stream replay”; Bilibili creator Zhugusheng Official; Watch the original video.
When splitting into two groups, check how much fire each faces. Send a pegasus to help if the lower route is struggling. Before killing an enemy blocking a path, check whether enemies behind it can then rush through.
Finish the first route and budget expedition time
I have already spent a long time on development, so this time I want to finish the first route before starting more. Staying in training, meals, and map exploration means I still have not seen the later story, and viewers may tire of it too.
Do not travel too far outside, either. Calculate whether you can arrive by the target date before planning a short expedition. Gathering along the way should not consume all the time before the next story event.
Avoid archers while splitting up for both devices
Enemies surround the battlefield, so my first thought is to bring more mobile units. Two Pegasus units can each reach a position that needs help. But a closer look shows many 
Archer enemies. Being able to fly there does not mean being able to stay safely.
Consider adding an archer while adjusting the team, then check starting positions and devices. The mission requires activating two launch devices simultaneously, so the whole team cannot simply chase nearby enemies. Watch the enemy movements first and assign each route accordingly.
Send mobile support when the lower route lacks units
Partway through, I realized the lower route seemed one person short while too many units were assigned above. Repeatedly changing the original attack order could not fill that gap.
Rewind two rounds and reassign the pegasus to help below. Units that can switch fronts quickly should reinforce the pressured side. Equal numbers on both routes do not guarantee both groups can handle their enemies.
After sending her over, check whether she actually contributes. High mobility gets her there quickly, but an unsuitable position or target can still leave her unhelpful for the entire battle.
Keep a blocking enemy alive to restrict a passage
Defeating the enemy in front may give those behind a path to approach. Before attacking, check which tile becomes empty and who can pass through it.
One target is easy to kill now, but removing him also opens the passage he blocks. Rather than finishing him immediately, leave him in place and handle other targets across the stairs. See whether you can draw enemies toward you.
Elsewhere, 
Cai is becoming isolated. Holding for one turn and trying to connect ranged support is better than continuing forward.
The final objective is to defeat all enemies, so both sides still need careful maneuvering. Before taking an available kill, consider the vacated tile and where enemies behind it can move. Sometimes a blocking enemy is also restricting the opponent's access for you.