Learn Hardcore Japanese: konkai ha basu de tosyokan ni ikimasu. - This time I will go to the library by bus.

は is the topic marker. By saying 今回は, you set “this time” as the topic of the sentence (“as for this time…”). It can also carry a slight contrastive nuance (“other times might be different, but this time…”).

What does the particle で after バス indicate?

In this context, で marks the means or method. バスで literally means “by bus,” telling us how you’re going to travel.

Why is に used after 図書館?

に after a place name marks the destination or goal of movement. So 図書館に行きます means “go to the library.”

Could I use へ instead of に after 図書館? What’s the difference?

Yes. 図書館へ行きます is also correct. Both に and へ can mark a destination. The nuance is that へ emphasizes movement toward the place, while に focuses more on arrival or the idea of going to that specific location. In many everyday contexts, they’re interchangeable.

Why is the verb 行きます in its polite form? What would the plain form be?

行きます is the masu-form, used to sound polite or formal. The plain (dictionary) form is 行く. So in casual speech you could say: 今回はバスで図書館に行く.

There’s no subject like “I” in the sentence. How do you know who is going?

Japanese often omits the subject when it’s clear from context. Here, since you’re talking about your own plans, “I” is understood. If you need to be explicit, you can add 私は at the beginning: 私は今回バスで図書館に行きます.

Is 行きます present tense or future tense? Does it mean “I go” or “I will go”?

In Japanese, the present (non-past) tense covers both present and future actions. Here, because of 今回 (“this time”) and the context of planning, 行きます is understood as “I will go” or “I’m going.”

What’s the difference between 今回 and 今度?

今回 (こんかい) strictly means “this time,” i.e. the current occasion.
今度 (こんど) can mean “this time,” but it often refers to “next time” or “sometime soon.”
So if you say 今度はバスで行きます, listeners might think you mean “next time.” To avoid ambiguity about “this current occasion,” 今回 is the safer choice.