From the top right platform, jump to the left into the thorns, then climb the left wall.

Requires:

{
  "thornHits": 1
}
{
  "or": [
    {
      "and": [
        "canUseIFrames",
        "canDash"
      ]
    },
    {
      "and": [
        {
          "tech": "canHorizontalDamageBoost"
        },
        "h_complexToCarryFlashSuit"
      ]
    },
    {
      "thornHits": 1
    }
  ]
}
"canWallJump"
{
  "not": "f_DefeatedPhantoon"
}
{
  "or": [
    "canRiskPermanentLossOfAccess",
    {
      "and": [
        "canDash",
        "canCarefulJump",
        {
          "disableEquipment": "HiJump"
        }
      ]
    },
    {
      "and": [
        "Gravity",
        "canDash"
      ]
    },
    {
      "and": [
        "canJumpIntoIBJ",
        "canBombHorizontally",
        "canTrickyJump"
      ]
    },
    {
      "and": [
        "Gravity",
        "canSpringBallJumpMidAir"
      ]
    },
    "canSpringFling",
    {
      "and": [
        "HiJump",
        "Gravity",
        "canInsaneJump"
      ]
    }
  ]
}

Dev note: The canCarefulJump and Gravity are here, as with either of those, there is access across with or without f_DefeatedPhantoon.