Postposition /ni/ 'to'

Robert will go to school.
(= Talking about Robert, he goes to school.)

• school --> がっこう（gakkou）
• Robert --> ロバートさん（robaato-san）
• will go; goes --> いきます　（いk-iます /ik-imas-u/）
• The event described by /ik/ 'goes; will go' has one role together with a relation describable with /to/ holding between the goal of the movement and the movement. The goer is the actor of the action described with /ik/.

Key 1: The form /ni/ describes the relation described basically by the preposition /to/ in English that holds between the goal of a movement and the movement. A postposition takes noun as its complement, i.e., immediately follow noun.

Key 2: There is no difference in the truth-conditional meanings between a clause with an order among a SUBJECT phrase, an OBJECT phrase, topic phrases, and postpositional phrases and another clause with a different order among them.

1)                                         がっこうに                      いきます。
                                            school-to                   goes
2)        ロバートさんは           がっこうに                      いきます。
           robaato-san-wa           gakkou-ni               ikimasu
           Robert-Mr.-TOPIC

The topic noun grammatically functions as its subject in this sentence since the subject phrase does not occur here. The topic noun cannot grammatically functions as its object since there is no an object phrase occurring. If you use /ga/ in place of /wa/, then the noun /robaato-san/ is interpreted as not topic.

I will return home.
(= I will return to my house.)

• home --> うち /uchi/ 'inside; my home' or いえ /ie/ 'house'

N.B. Neither of the words /uchi/ and /ie/ can be adverb as English 'home' is, and so /uchi/ and /ie/ are always both noun.
• Mary --> メアリーさん（mearii-san）
• The event described by /kaer/ 'goes; will go' has one role together with a relation describable with /to/holding between the goal of the movement and the movement. The goer is the actor of the action described with /ik/.