To avoid heavy Rinka damage, you must perform the Crystal Flash on a specific tile: on the third floor tile from the left wall. Lay the Power Bomb immediately after destroying both Rinkas.

Requires:

{
  "obstaclesCleared": [
    "A"
  ]
}
"h_canCrystalFlash"
{
  "enemyDamage": {
    "enemy": "Rinka",
    "type": "contact",
    "hits": 1
  }
}