In the Brighter Together: Our Grand Concert scenario, a training week can look crowded and still fail to produce the rainbow run that pushes a build toward Speed 1600. Three cards may sit on the Speed facility, but if none is glowing rainbow, the session misses the multiplicative payoff that separates a capped stat line from an ordinary one. The decisive fact is mathematical, not mystical: two 25% Friendship Bonuses multiply to 1.25 × 1.25 = 1.5625, a 56.25% increase, not a 50% addition. In the October 2026 Grand Concert meta, that difference determines whether Speed 1600 is a realistic target or a hopeful accident.

What Friendship Bonus Actually Is

Rainbow Training triggers only when both conditions are true: the Support Card stands on its matching Specialty facility, and its Bond Gauge is 80 or higher, indicated by the orange glow. If either condition fails, that card contributes zero Friendship multiplier for the session. When multiple qualifying cards share one facility, they activate together as a rainbow stack.

The stack is multiplicative. Two cards with 25% each produce 1.25 × 1.25 = 1.5625. Three cards at 30% produce 1.3 × 1.3 × 1.3 = 2.197, a 119.7% increase over base. Players should confirm each card's exact percentage in the in-game card detail screen or through current official information, because outdated tier-list screenshots often misstate the values that matter most.

The Training Gain Formula in Practice

A practical model for planning is:

Total Gain = floor(Base Value × Friendship Multiplier × Motivation Multiplier × Training Effectiveness Multiplier × Scenario Multiplier)

The floor applies after all multipliers are combined, so a large rainbow stack can change the final integer more than a small additive bonus. In Grand Concert, Concert Link and other scenario effects belong to the multiplicative scenario component.

Separate additive categories from true multipliers when comparing cards. Friendship Bonus and Scenario Multiplier multiply across categories, while Motivation bonuses such as Perfect 1.2× and Training Effectiveness bonuses such as 10% or 15% add within their respective categories. Consequently, a three-card 30% rainbow reaches 2.197× base, the kind of spike that makes Speed 1600 realistic instead of merely hoping for favorable training rolls.

Deck Synergy for the Grand Concert Meta

For the October 7, 2026 Grand Concert meta, build around 3 Speed / 2 Guts / 1 Friend. Anchor Speed with SSR Kitasan Black (Fire at My Heels) for Specialty Rate and consistent rainbows. Use SSR Yaeno Muteki (Guts) as a late-game power card whose key Friendship value is gated at 100 Bond. SSR Light Hello fills the Friend slot, supporting Energy management and Concert Link bonuses.

Accelerate the opening with SSR Oguri Cap (Wit) when available. Its unique Initial Bond boost raises other cards' starting Bond and gets more of the deck toward the 80-Bond rainbow threshold sooner. Keep total Race Bonus at 35–50%, because Grand Concert's race rewards are part of the final stat economy. For UC-rank targets, prioritize Friendship cards that also carry Skill Point Bonus; Skill Points are the hidden bottleneck even when Speed and Guts are already capped.

Spending Resources Wisely

Plan banner pulls around scenario-linked value rather than isolated Friendship percentages. Prioritize Smart Falcon, Agnes Tachyon, Silence Suzuka, Mihono Bourbon, and Light Hello when their Concert Link effects fit the roster, since designated characters activate the relevant scenario multipliers. The community Spark threshold is 200 Exchange Points, equal to 30,000 Carats, the premium currency used for these pulls.

Before labeling a card top tier, check event reliability and the agemasen risk. A failed event that withholds a card's key Gold Skill can cripple the finished build even when its Friendship Bonus is excellent. Spend only after confirming the card's event chain, Link role, Specialty value, and whether it supports the 35–50% Race Bonus target. No publicly verifiable data is available for unsupported event-success probabilities.

Quick Reference: Top Synergy Cards and Next Steps

Bookmark current official seasonal notes for changes to Scenario Info rewards, because Concert Link bonuses can shift across update cycles. Then use this three-point checklist before Champions Meetings prep:

• ✅ Verify 80+ Bond before Turn 30.

• ✅ Bring at least 3 Specialty-matched cards.

• ✅ Treat Speed 1600 as the primary benchmark.

A glowing three-card rainbow is not luck alone. It is the payoff for arranging every multiplier before the training week arrives. In the 2026 Grand Concert environment, the players who understand multiplicative Friendship Bonus stacking, Bond timing, and scenario-linked deck roles are the ones who turn a crowded Speed facility into a genuine Speed 1600 run.