Database

[{"name":"Biology Book","data":{"toc":{"_version":"1","ge":[{"_name":"The Fundamental Unit of Life","_id":"5a","ge":[{"_value":"Living Organisms","_id":"5b"}]}]}}},{"name":"Biology Book 2","data":{"toc":{"_version":"1","ge":[{"_name":"The Fundamental Unit of dead","_id":"5a","ge":[{"_value":"Non-living Organisms","_id":"5c"}]}]}}}]

Query

db.collection.aggregate([{$match:{"data.toc.ge.ge._id":"5b"}},{$unwind:"$data.toc.ge"},{$unwind:"$data.toc.ge.ge"},{$group:{_id:null,book:{$push:"$data.toc.ge.ge._value"}}},{$project:{_id:0,first:{$arrayElemAt:["$book",0]},}}])

Result