(X) + tomonaruto is used when a situation or thing expressed by (X) is perceived as special. This meaning comes from the use of the particle mo as in: a. 夜も更けていた (It was late at night) b. 夏も終わってしまった (Summer is over now)
Note that the speaker feels special about yoru "night" in a. or natsu "summer" in b.
mo can be omitted from tomonaruto but it takes away the special significance