TSE:3350 · Metaplanet Inc.
Is Metaplanet Bitcoin quantum-exposed?
Metaplanet holds approximately 5,000 BTC as of May 2025, custodied with SBI VC Trade. Metaplanet does not publish address-level proof of reserves, so quantum exposure is estimated by applying the project-wide bucket distribution to disclosed holdings.
5,000 BTC · AS OF 2025-05-31 · SOURCE: Metaplanet IR May 2025 update
Three-bucket breakdown
Key visible on-chain (Taproot, reused legacy)
Periodic key exposure via hot-wallet rotation
Hash-only outputs, key hidden until first spend
Custodians
- SBI VC Trade, No public post-quantum migration roadmap as of 2025.
Under the supply-wide distribution, roughly 1,250 BTC of Metaplanet's stack sits in the structural bucket where keys are already visible on-chain, 250 BTC in the operational bucket, and 3,500 BTC in hash-only outputs that are not key-exposed today.
The estimate is sensitive to SBI VC Trade's actual script-type mix. A Japanese regulated custodian may concentrate in legacy or SegWit hash-output addresses, which would shift more of the stack toward the protected bucket. Until the custodian publishes a breakdown, the supply-wide distribution is the most honest available benchmark.
For investors weighing Metaplanet's mNAV premium, the relevant question is whether SBI VC Trade has a credible PQC migration plan. As of 2025 no such plan has been published.
FAQ
Is Metaplanet's Bitcoin at immediate risk?
No. No working quantum computer can break secp256k1. The estimate is about long-horizon custody, not present-day vulnerability.
Why one custodian instead of several?
Metaplanet's filings disclose SBI VC Trade as the primary custodian. If a second custodian is engaged in the future, the bucket distribution may change.
How is 5,000 BTC sourced?
Metaplanet's May 2025 IR update is the cited disclosure. Holdings change frequently as the company adds. Treat the number as a snapshot.
What this leaves out
secp256k1 is unbroken. This page is about long-horizon migration sizing, not present-day vulnerability. The three-bucket split assumes the company's coins follow the project-wide script-type distribution, which is an approximation. Custodian-specific concentration in Taproot, reused legacy, or hash-only outputs can move the structural bucket by tens of percentage points. The model does not account for multisig quorum exposure, cold-storage rotation cadence, or non-public migration plans.