What's the best way to level up a Brave Burst?

Question

When I'm going to fuse a unit, some units used as ingredient can upgrade the Brave Burst skill of the Base unit.

But what's the best way to do this upgrade? Fuse each unit separately or get 5 ingredient units and fuse it together?

Answer 1

From the wiki:

During fusing, each unit with the same type of Brave Burst used in the fusion has a small chance to increase the base unit's Brave Burst level. There are 3 types so far:

Offensive Brave Bursts (damage single or everyone) Healing Brave Bursts Stat boosting Brave Bursts, which I call Support (e.g., increase ATK, crit, etc.) Let's say you have a Fire God Vargas with Brave Burst level 1. His BB is an offensive type, since it inflicts damage. If you fuse 5x Metal Gods into him, he has ZERO chance to increase his BB levels because the Metal Gods are not of the same type of Brave Burst (they actually have no Brave Burst). Now let's say that you fuse 5x Pikeman Lances. Since Pikeman Lance does have an offensive Brave Burst, then there is a chance that Vargas' BB level will increase, multiple times even. Personally,I've gone from 1 to 4 during a single fuse session.

What I don't know:

Does the element of the fused unit matter for increased chances of BB level up? I think so, but not confirmed. I've seen 3 BB level increases from a single fuse using slimes Does the chance diminish as the Brave Burst level gets higher? Does the rarity of the unit being consumed matter? Does the level of the unit being consumed matter? Confirmed:

ELEMENT of fused unit matter a little for increasing the chances of BB level up. The rarity of unit being consumed only matter a little. Level of unit being consume doesnt matter Fusing the same unit ( Great Sage Mimir + Sage Mimir ) increases the chance of BB leveling up.

Some tips:

Evolving a unit resets its Brave Burst back half of the previous Brave Burst level (For example, a Vargas with Brave Burst level 10, it will become level 5 when he evolved into Burning Vargas). And if the level is at the odd number (Example : 9) it will be halved into lower half (into level 4). Don't focus on leveling Brave Burst until the unit has reached its maximum evolution. Note that future updates may introduce higher levels of evolution for specific units! If you're going to focus on leveling Brave Burst, start early when it's cheap! Save those high-XP fuse unit (e.g., Metal Kings) for after you've hit BB Lvl. 10. Use the weekend to amass zel from the Weekend dungeon. You're gonna need a lot of money!

It seems to me that the fusion of 5 ingredient units and fusing them together will be the best bet. Because you are doing it in bulk the exp will be far greater than just slowly leveling each unit individually.