How do we translate/simulate the package concept from JAVA to CPP using the 'using' or 'namespace' keywords?

See more:

C++

Java

package concept in JAVA;
1. By default all classes/func/members with in the same package, they can access each other symbols/data, aside from tagged private access modifiers, and without explicitly importing them.
2. ...
3. ...
...

What I have tried:

We only need concept number #1, and it is ok if we cannot implicitly import/using a package/namespace, so I tried this.

namespace com::tut::cpp {
    using com::tut::cpp::Derive; //REM: I tried applying: using-declarations or using-directives
    class Base {
    public:
        Base();
        virtual ~Base();
        Derive& funcBase(); //REM: it return a instantiated Derive class
    };

    class Derive : public Base {
    public:
        Derive();
        ~Derive() override;
    };
}


//REM: Definition
com::tut::cpp::Base::Base() {}
com::tut::cpp::Base::~Base() {}
com::tut::cpp::Derive& com::tut::cpp::Base::funcBase() {
    static com::tut::cpp::Derive d;
    return d;
}

com::tut::cpp::Derive::Derive() {}
com::tut::cpp::Derive::~Derive() {}

And we would like to separate them into different files, such as;

//Base.h
#include "Derive.h"
//using com::tut::cpp::Derive; //REM: is it possible to do this outside?
namespace com::tut::cpp {
    using com::tut::cpp::Derive;
    class Base {
    public:
        Base();
        virtual ~Base();
        Derive& funcBase();
    };

}

//Derive.h
#include "Base.h"
namespace com::tut::cpp {
    class Derive : public Base {
    public:
        Derive();
        ~Derive() override;
    };
}

//Body.cpp
#include "Base.h"
#include "Derive.h"
//REM: Definition
com::tut::cpp::Base::Base() {}
com::tut::cpp::Base::~Base() {}
com::tut::cpp::Derive& com::tut::cpp::Base::funcBase() {
    static com::tut::cpp::Derive d;
    return d;
}

com::tut::cpp::Derive::Derive() {}
com::tut::cpp::Derive::~Derive() {}