Learn Hardcore Japanese: karesi to ha, ryouri toka geemu toka wo sinagara rusuban wo suru zikan ga itiban tanosii desu. - With my boyfriend, the most fun time is when we house-sit together while cooking, playing games, and so on.

“As for (the time) with my boyfriend…”
Nuance: it lightly contrasts time with my boyfriend with time spent with other people or in other situations.

Compare:

彼氏と、料理とかゲームとかをしながら留守番をする時間が一番楽しいです。
→ The time when I stay home with my boyfriend … is the most fun. (neutral)
彼氏とは、料理とかゲームとかをしながら留守番をする時間が一番楽しいです。
→ As for when I’m with my boyfriend, that time is the most fun (more than other times).

So X + と + は is a common pattern when you want to say “as for being with X…”, often with a contrastive feel:

友達とは、日本語で話します。
As for (when I’m) with friends, I speak in Japanese.

In 彼氏と, does と mean “and” or “with”? How is it different from English?

In 彼氏と, と means “with”:

彼氏と留守番をする
to stay home (do house-sitting) with my boyfriend

The same と is also used for “and” when listing things:

りんごとバナナ – apples and bananas

So と can mean either “with” (for companions) or “and” (for lists) depending on context. In this sentence:

彼氏と → “with my boyfriend,” not “boyfriend and (someone/thing else)”

What does 留守番をする mean exactly? Is it just “to stay at home”?

留守番をする literally means “to do house-sitting / to guard the house while others are out.”

Nuance:

You stay home while someone else is away, often to:
- watch the house,
- look after kids or pets,
- receive deliveries, etc.

In everyday speech, it often just feels like “staying home (while others are out),” but it has more purpose than simply 家にいる (just being at home).

So in context:

彼氏とは、料理とかゲームとかをしながら留守番をする時間が一番楽しいです。
→ The time when I stay home (look after the house) with my boyfriend, doing things like cooking and gaming, is the most fun.

What does とか mean in 料理とかゲームとか? Why is it used twice?

とか is a colloquial particle that, in this kind of list, means “things like A, B, and so on.”

料理とかゲームとか → things like cooking, gaming, etc.

Points:

とか after each item makes the list feel:
- casual / conversational,
- non‑exhaustive (“and stuff like that”).
The second とか (after the last item) is not required, but very natural in spoken style:
- 料理とかゲームとかをする – very casual
- 料理とかゲームをする – also OK; a bit less “bouncy”

It’s similar in function to AやB(や), but:

や is a bit more neutral/formal: 料理やゲームをする。
とか sounds more casual/colloquial: 料理とかゲームとかをする。

Why is there only one を after 料理とかゲームとか, and not after each noun?

The を at the end attaches to the whole list:

料理とかゲームとかをしながら
→ literally “while doing things like cooking or gaming.”

In Japanese, you usually put the case particle only once at the end of the entire list:

りんごやバナナを食べる。
not ✕りんごをやバナナを食べる。

Same pattern here:

料理とかゲームとかをする
to do things like cooking and gaming

That entire phrase is the object of する, so を comes once, right before する / しながら.

How does しながら work here? Is it “while doing A and B, I do C”?

Yes. 〜しながら means “while doing ~” (simultaneous actions).

The structure here is:

料理とかゲームとかをしながら
(while doing things like cooking and gaming)
留守番をする
(I stay home / house‑sit)

So it means:

While doing things like cooking or playing games, I stay home (and look after the house).

You can think of it as:

料理とかゲームとかをする＋ながら → 料理とかゲームとかをしながら

Note:

Only the first action takes ながら.
The main verb is 留守番をする (in plain form here, embedded in a larger phrase).

How does the part before 時間 work? What exactly is modifying 時間 here?

Everything before 時間 (except the comma) forms one long relative clause that modifies 時間:

[彼氏とは、料理とかゲームとかをしながら留守番をする]時間

So the structure is:

彼氏とは、料理とかゲームとかをしながら留守番をする
→ to stay home with my boyfriend, doing things like cooking and gaming
時間
→ the time (when I do that)

Put together:

彼氏とは、料理とかゲームとかをしながら留守番をする時間
→ the time when I stay home with my boyfriend, doing things like cooking and gaming

Then:

…時間が一番楽しいです。
→ that time is the most fun.

So the core sentence is:

（その）時間が一番楽しいです。 – That time is the most fun.
with その時間 being specified by the long relative clause before it.

Why is が used after 時間 instead of は?

Here, が marks 時間 as the subject of the adjective 楽しい:

時間が楽しいです。
The time is fun.

Using が puts focus on which thing is fun:

（その）時間が一番楽しいです。
→ That time is the most fun (out of all times).

If you said:

時間は一番楽しいです。

it could sound more like you’re introducing “as for that time…” as the topic, which is possible but slightly shifts nuance. In sentences with:

an adjective (楽しい、うれしい、悲しい) and
a “which-one” type idea (一番, 一番〜, いちばん…),

が is very common, because you’re identifying which thing has that quality.

So: 時間が一番楽しいです = That time is the most fun (among alternatives).

What does 一番 add to 楽しい here?

一番 (いちばん) means “the most / number one / the best”.

楽しい – fun / enjoyable
一番楽しい – the most fun

So:

時間が楽しいです。
→ That time is fun.
時間が一番楽しいです。
→ That time is the most fun (compared to other times or activities).

In English, you can translate 一番楽しいです as:

is the most fun, or
is my favorite (time), depending on context.

Why is there no “my” in 彼氏, but we still translate it as “my boyfriend”?

Japanese usually omits possessive pronouns like “my,” “your,” when context makes it obvious.

彼氏 literally just means “boyfriend.”
In a sentence like this, the default assumption is “my boyfriend” because:
- the speaker is talking about their own experiences and feelings,
- mentioning staying home, doing fun things, etc.

So:

彼氏とは〜時間が一番楽しいです。
→ Naturally understood as The time when I’m with *my boyfriend is the most fun.*

If you really needed to specify “my,” you could say:

私の彼氏 – my boyfriend

but in normal conversation, 彼氏 alone is enough.

Could you say 彼氏と一緒に instead of 彼氏とは? Would the meaning change?

You could say:

彼氏と一緒に、料理とかゲームとかをしながら留守番をする時間が一番楽しいです。

This means:

The time when I stay home with my boyfriend (together), doing things like cooking and gaming, is the most fun.

Differences in nuance:

彼氏と一緒に
- Explicitly emphasizes “together with my boyfriend.”
- Fairly neutral; no strong contrast.
彼氏とは
- Emphasizes “as for (time) with my boyfriend”, with a mild contrast:
  - more fun than time with other people,
  - more fun than other kinds of time.

Both are correct; 彼氏とは feels a bit more like you’re highlighting “time with him specifically.”

Is the comma after は important? Does it change the meaning?

The comma after 彼氏とは is mostly for readability and natural rhythm:

彼氏とは、料理とかゲームとかをしながら〜

Spoken Japanese naturally pauses there, so the comma reflects that. Without the comma:

彼氏とは料理とかゲームとかをしながら〜

is still grammatically correct, just a bit harder to read at a glance. The meaning doesn’t change; it just marks a natural pause after the topic (彼氏とは).